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 RC1 82 .C36 The mode of infectio 
 
 RECAP 
 
 FisKE Fund Prize Dissertation. No. LII 
 
 The Mode of Infection 
 
 AND 
 
 Duration of the Infectious Period 
 
 IN 
 
 Scarlet Fever. 
 
 NIOXTO : 
 
 Dextrae se nostra Scientia 
 Implicuit, sequiturque Verum non passibus acquis. 
 
 CHARLES V. CHAPIN, M. D., 
 Providence, R. I. 
 
CoHese of l^^psikimsi anti burgeons: 
 itibrarp 
 
Digitized by the Internet Archive 
 
 in 2010 with funding from 
 
 Open Knowledge Commons 
 
 http://www.archive.org/details/modeofinfectiondOOchap 
 
FisKE Fund Prize Dissertation. No. LII. 
 
 The Mode of Infection 
 
 AND 
 
 Duration of the Infectious Period 
 
 Scarlet Fever. 
 
 NIOTTO : 
 
 Dextrae se nostra Scientia 
 Implicuit, sequiturque Verum non passibus acquis. 
 
 BY 
 
 CHARLES V. CHAPIN, M. D., 
 Providence, R. I. 
 
 PROVIDENCE: 
 Snow & Fakhnam Company, Printers. 
 1909. 
 
-RC!^^ 
 
THE Trustees of the Fiske Fund, at the annual meeting of the 
 Ehode Island Medical Society, held at Providence, June 1, 1909, 
 announced that they had awarded a premium of two hundred ($200) 
 to an essay on " The Mode of Infection and Duration of the In- 
 fectious Period in Scarlet Fever," bearing the motto : 
 
 " Dextrae se nostra Scientia 
 Implicuit, sequiturque Verum non passitous acquis." 
 
 The author was found to be CHAKLES V. CHAPIN, M. D., 
 of Providence, R. I. 
 
 DR. FRANK B. FULLER, Providence, 
 
 DR. EUGENE KINGMAN, 
 
 DR. A. A. MANN, Central Falls, 
 
 Trustees. 
 
 HALSEY DeWOLF, M. D., Providence, 
 
 Secretary of the Trustees. 
 
The Mode of Infection and Duration of the 
 Infectious Period in Scarlet Fever. 
 
 It is much to be regretted that the specific organism 
 which is doubtless the cause of scarlet fever has not 
 as yet been identified. Various observers have from 
 time to time, described cocci, or bacilli, which they 
 believed, or suspected to be, the cause of the disease. 
 Klein isolated a diplococcus which for a while was 
 thought by many to be the specific germ, but his 
 observations have not stood the test of time, and 
 neither have those of Class, who later also reported a 
 diplococcus as the vera causa. More recently Mallory 
 (1) described certain bodies in the skin of scarlet fever 
 patients which he believed to be protozoa, and which 
 he suspected might stand in causative relation to the 
 disease, and within a few months Gamaleia (2) has also 
 reported finding protozoan forms constantly present. 
 The findings of these last two observers have not as 
 yet been verified. At present therefore we can only 
 employ clinical or epidemiological methods, in the in- 
 vestigation of scarlet fever, and such methods are 
 difficult, and by themselves are unlikely to yield 
 decisive results. 
 
6 THE MODE OE INFECTION AND DURATION OF 
 
 Before proceeding to the discussion of the subject, 
 it is perhaps well to call attention to the analogy which 
 has been supposed to exist between scarlet fever and 
 smallpox. There is a good deal of desquamation, as 
 well as shedding of the crusts, in smallpox, and these 
 crusts, and presumably the epidermis also, are infec- 
 tious. The desquamation in scarlet fever has been 
 believed to be similar in nature to that of smallpox, 
 due to the active working of the specific poison in the 
 skin, and therefore also infectious. 
 
 A more careful study of scarlet fever has led many 
 to see that this resemblance is superficial merely, and 
 that scarlet fever seems to be much more like diphtheria 
 than any other disease. The age incidence of the two 
 diseases is about the same, as is also the degree of 
 infectivity. The period of incubation is nearly the 
 same. A long latent period may often be noted in 
 each. Both diseases begin with sore throat, and the 
 throat symptoms are usually the most prominent 
 symptoms, and are so nearly alike in the two diseases 
 that except for the rash in the one case, and the find- 
 ing of diphtheria bacilli in the other, it is difficult in 
 most cases to make a diagnosis. In fact many cases of 
 scarlet fever are before the e^ppearance of the rash, 
 considered to be diphtheria. In both diseases albumi- 
 nuria and middle ear inflamation are common. Both 
 diseases are infectious at the very beginning, and the 
 infectivity gradually disappears in a few weeks, b;it in 
 
THE INFECTIOUS PERIOD IN SCARLET FEVEK. 7 
 
 some instances may be retained for months, and often 
 this infectivity seems to be connected with a chronic 
 rhinitis. Scarlet fever seems to be as much a local 
 disease of the throat as is diphtheria. The eruption in 
 scarlet fever appears much more likely to be the 
 result of a toxemia, than to an actual invasion of the 
 skin by the parasite, as is the case in smallpox. 
 
 It will be more convenient to consider the duration 
 of infectivity first, and modes of infection afterwards, 
 and as a preliminary step we may inquire as to the 
 duration of incubation, for without some knowledge of 
 this, it is difficult to determine what period of the 
 disease is infectious. 
 
 The word incubation as here used, merely means the 
 time which elapses between the implantation of the 
 infectious material and the development of the initial 
 symptoms. It is true, incubation carries with it the 
 idea that the virus of the disease must of necessity 
 have a more or less definite interval in which to multi- 
 ply and perhaps pass through a certain portion of a 
 more or less complicated life cycle. But in a number 
 of infectious diseases, such as diphtheria, it is known 
 with a fair degree of certainty that this is not so. In 
 some cases as soon as diphtheria bacilli are planted on 
 a mucous surface they begin to proliferate and produce 
 toxins, and probably if our vision were acute enough 
 could be seen to cause tissue changes within a remark- 
 ably short time. Certainly quite marked pathological 
 
8 THE MODE OF INFECTION AND DURATION OF 
 
 conditions are sometimes noticeable in a few hours. 
 This has particularly been the case in those laboratory 
 infections where the moment of implantation was 
 known, and where the symptoms were carefully 
 watched. 
 
 According to most observers the incubation of scarlet 
 fever is usually short, in most instances a few days only. 
 A committee of the Boston Society of Medical Improve- 
 ment, appointed to consider the subject, reported (o) 
 that the period of incubation in scarlet fever is as a rule 
 two or three days, but may be extended to eight days, 
 and possibly twenty (McCollom). Reference is made 
 by the above committee to Murchison (4) who collected 
 reports of 75 cases in which the period of incubation 
 in 73 could not have been over 5 days, in 54 it could 
 not have been over 4 days, in 20 not over 3 days, in 
 15 not over 2 days, and in three instances it could not 
 have exceeded 24 hours. The committee quote from 
 a dozen or more writers whose observations and opinions 
 are in entire accord with Murchison's. Thus Reimer 
 found that in two thirds of 3,624 cases the disease 
 developed within the first three days after exposure. 
 
 The writer's experience has led him to concur in the 
 conclusions as stated above, that is, that the period of 
 incubation is usually only a few days, and that it may 
 be only a few hours. This conclusion is based upon 
 First; the time when secondary cases develop in the 
 family. Second ; the time when other families in the 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 9 
 
 same house develop the disease. Third; the time when 
 cases develop in the family after return from the hos- 
 pital. Fourth ; the time when well children sent away 
 from home sicken with the disease while away or after 
 their return, and Fifth ; a few special instances. Tables 
 illustrating the first two points are given on pages 12 
 and 13. 
 
 Hospital return cases from my own experience are 
 not very numerous, but the facts correspond with the 
 English data given by Cameron and Turner. In the 
 latter's experience 441 of 1,129 ''return cases" of 
 scarlet fever occurred in the first week. Of my own 41 
 observed cases 23 were in the first week after return. 
 Of 52 well persons who were removed from scarlet 
 fever houses under my observation, and who were 
 afterwards taken sick, 29 developed the disease during 
 the first week. 
 
 While it is possible that in the majority of cases of 
 scarlet fever the period of incubation is only a few 
 days, it may be prolonged perhaps for weeks. We 
 know that the period of incubation is usually short in 
 diphtheria, but that sometimes a person may harbor 
 diphtheria bacilli in throat or nose for weeks, and yet 
 remain perfectly well, and then finally the disease will 
 develop. It is probable that precisely the same thing 
 happens in scarlet fever. Welch and Schamberg (5) 
 quote Hagenbach-Burchhardt and Holt as reporting 
 many cases of prolonged incubation some extending as 
 
10 THE MODE OF INFECTION AND DURATION OF 
 
 long as 21 days. It is probable that from a pathological 
 standpoint, incubation in scarlet fever has little meaning. 
 The fact that cases returning from a hospital may be 
 slow in infecting the family, or that well members of 
 the family returning home after the termination of 
 isolation, may not quickly develop the disease, probably 
 means that in these instances the virus of the disease 
 is small in amount, or is not thrown off continuously 
 from the infecting case. Thus an intermittently dis- 
 charging ear would readily explain cases of delayed 
 infection or what would apparently be prolonged 
 incubation. 
 
 DURATION OF THE INFECTIOUS PERIOD. 
 
 There is much evidence to show that scarlet fever is 
 infectious in the early stages, particularly during the 
 height of the throat symptoms. A considerable num- 
 ber of cases are on record where a person exposed to 
 scarlet fever during this period contracted the disease. 
 Several of these are mentioned on pages 23 and 25 of 
 this essay. This evidence from individual cases is also 
 in accord with much statistical evidence. The follow- 
 ing tables prepared by the writer show, 
 
 First, The time at which secondary infections occur 
 in the family. 
 
 Second, The time at which other families in the 
 house become infected. 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. H 
 
 These tables indicate that in a large proportion of 
 the families the infection of others takes place during 
 the first week of the disease. This would scarcely be 
 possible unless the period of incubation was short and 
 the disease infectious in the early stages. 
 
12 
 
 THE MODE OF INFECTION AND DURATION OF 
 
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THE INFECTIOUS PERIOD IN SCARLET FEVER. 
 
 13 
 
 TABLE n. SCARLET FEVER. 
 
 Time of Infection of Other Families ia House. 
 
 
 
 
 
 After Termination of Isolation. 
 
 
 During ] 
 
 Period of Isola- 
 FiRST Sickness. 
 
 
 
 
 
 
 TION OF 
 
 Dav of Initial Sickness. 
 
 Day of Release from 
 Isolation. 
 
 .2 
 
 ■+-( 
 
 .y 
 
 4h 
 
 
 
 
 
 
 <^ 
 
 
 <H 
 
 ■w . 
 
 o 
 
 t> 
 
 
 
 i 
 
 
 
 
 
 
 
 
 
 
 
 11 
 
 B6 
 
 
 ''- CO 
 
 1 
 
 
 
 a 
 
 
 
 1 
 
 CIS 
 
 la 
 
 ?? 
 
 a) 03 
 
 ia 
 
 
 « 
 
 a 
 
 12; 
 
 
 
 
 
 Q 
 
 12; 
 
 a 
 
 z 
 
 1 
 
 9 
 
 38 
 
 1 
 
 : 1 
 
 
 38 
 
 
 1 
 
 1 
 
 38 
 
 
 2 
 
 6 
 
 39 
 
 
 2 
 
 
 39 
 
 i" 
 
 2 
 
 1 
 
 39 
 
 
 3 
 
 6 
 
 40 
 
 .... 
 
 i 
 
 
 40 
 
 
 3 
 
 
 40 
 
 i 
 
 4 
 
 3 
 
 41 
 
 
 i '^ 
 
 
 41 
 
 
 4 
 
 i 
 
 41 
 
 
 5 
 
 7 
 
 42 
 
 2 
 
 ! 5 
 
 
 42 
 
 
 5 
 
 
 42 
 
 
 6 
 
 4 
 
 43 
 
 . . . . 
 
 i 6 
 
 
 43 
 
 "'i' 
 
 6 
 
 .... 
 
 43 
 
 
 7 
 
 2 
 
 44 
 
 i" 
 
 7 
 
 
 44 
 
 
 7 
 
 
 44 
 
 
 8 
 
 4 
 
 45 
 
 1 
 
 8 
 
 
 45 
 
 
 8 
 
 
 45 
 
 
 9 
 
 2 
 
 46 
 
 '! 
 
 i 9 
 
 
 46 
 
 
 9 
 
 1 
 
 46 
 
 
 10 
 
 1 
 
 47 
 
 .... 
 
 ilO 
 
 
 47 
 
 i' 
 
 10 
 
 3 
 
 47 
 
 
 11 
 
 1 
 
 48 
 
 
 111 
 
 
 48 
 
 
 11 
 
 
 48 
 
 
 12 
 
 3 
 
 49 
 
 
 112 
 
 
 49 
 
 "2" 
 
 12 
 
 
 49 
 
 .... 
 
 13 
 
 4 
 
 50 
 
 
 [13 
 
 
 50 
 
 
 13 
 
 
 50 
 
 
 14 
 
 2 
 
 51 
 
 
 !14 
 
 
 51 
 
 * • ■ > 
 
 14 
 
 
 51 
 
 .... 
 
 15 
 
 
 52 
 
 "i" 
 
 |15 
 
 
 52 
 
 
 15 
 
 
 52 
 
 
 16 
 
 
 53 
 
 1 
 
 ;16 
 
 
 53 
 
 
 16 
 
 
 63 
 
 1 
 
 17 
 
 l' 
 
 54 
 
 1 
 
 il7 
 
 
 54 
 
 
 17 
 
 2' 
 
 54 
 
 
 18 
 
 
 55 
 
 • • ■ • 
 
 il8 
 
 
 55 
 
 ' 2 
 
 18 
 
 
 55 
 
 .... 
 
 19 
 
 
 56 
 
 . . . ■ 
 
 jl9 
 
 
 56 
 
 
 19 
 
 
 56 
 
 
 20 
 
 1 
 
 57 
 
 
 !20 
 
 '2' 
 
 57 
 
 "i' 
 
 20 
 
 
 57 
 
 
 21 
 
 
 58 
 
 
 '21 
 
 
 58 
 
 
 21 
 
 "i" 
 
 58 
 
 "i" 
 
 22 
 
 "i" 
 
 59 
 
 .... 
 
 I22 
 
 
 59 
 
 i 
 
 22 
 
 
 59 
 
 
 23 
 
 .... 
 
 60 
 
 
 !23 
 
 
 60 
 
 1 
 
 23 
 
 .... 
 
 60 
 
 .... 
 
 24 
 
 
 Srcl mo. 
 
 2 
 
 24 
 
 
 3rd mo. 
 
 11 
 
 24 
 
 
 3rd. mo. 
 
 8 
 
 25 
 
 1 
 
 4tli " 
 
 
 25 
 
 
 4th " 
 
 6 
 
 25 
 
 
 4th " 
 
 2 
 
 26 
 
 1 
 
 5th '•■ 
 
 
 126 
 
 
 5th '' 
 
 
 26 
 
 
 5th " 
 
 
 27 
 
 
 6th " 
 
 
 27 
 
 
 6th " 
 
 1' 
 
 27 
 
 .... 
 
 6th " 
 
 2 
 
 28 
 
 '2' 
 
 7th " 
 
 
 28 
 
 
 7th " 
 
 3 
 
 28 
 
 
 7th " 
 
 3 
 
 29 
 
 1 
 
 8th " 
 
 
 29 
 
 
 8th " 
 
 1 
 
 29 
 
 1 
 
 8th " 
 
 .... 
 
 30 
 
 2 
 
 9th " 
 
 
 I30 
 
 
 9th " 
 
 
 30 
 
 1 
 
 9th " 
 
 
 31 
 
 . . . • 
 
 10th " 
 
 
 |31 
 
 ""i" 
 
 10th " 
 
 
 31 
 
 
 10th " 
 
 "i' 
 
 32 
 
 
 11th ^'■ 
 
 
 32 
 
 
 11th *' 
 
 i' 
 
 32 
 
 "i' 
 
 11th '' 
 
 .... 
 
 33 
 
 
 12 th " 
 
 
 133 
 
 
 12th •' 
 
 . . . • 
 
 33 
 
 
 12th " 
 
 
 34 
 
 
 
 
 34 
 35 
 
 1 
 
 13th '' 
 
 1 
 
 34 
 
 35 
 36 
 
 37 
 
 
 
 
 35 
 
 2" 
 
 1 
 
 
 
 
 
 
 36 
 
 
 
 36 
 
 37 
 
 
 38 
 
 .... 
 
 
 
 
 37 
 
 
 
 
 
 
 
 
 
 
 
 
 
 80 1 
 
 38 
 
14 THE MODE OF INFECTION AND DURATION OF 
 
 That the infectivity is at its height during the early 
 days of the disease, and that it diminishes quite rapidly 
 after the disappearance of the throat symptoms and 
 the rash, also seems to be indicated by the data just 
 given. This however is contrary to the popular 
 notion, for most of the laity, and many physicians, 
 consider that scarlet fever is much more infectious dur- 
 ing desquamation than at any other time. As will be 
 shown when discussing the infectiousness of the ex- 
 foliated epidermis there does not appear to be any 
 experimental or clinical evidence of this. Yet it must 
 be admitted that while the facts of rapidly diminish- 
 ing extension of the disease in and out of the family, 
 is in accord with the view that the infectivity also 
 rapidly diminishes after the disappearance of the acute 
 symptoms, it is not a proof of it, for the decreasing 
 number of cases in the family may be due to the using 
 up of all susceptible material, and failure to extend 
 beyond the family may be due, in part, as seems to 
 the writer probable, to the success of the isolation 
 which is enforced as soon as the cases are recognized. 
 But surely there is nothing in these facts to indicate a 
 greater degree of infectiousness during the later than 
 during the earlier stages of the disease. 
 
 The following facts do indicate quite clearly the 
 diminishing infectivity during the later stages. I 
 have records of the removal of 493 well children from 
 families where there was scarlet fever, showing the 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 15 
 
 time at which they returned. Unfortunately I made 
 no record of cases that returned home within a week, 
 but probably these would have shown an equal or 
 even higher incidence of the disease. 
 
 Number of Weeks Away. Over Un- Total 
 
 12345677 kaown. Children. 
 
 Children who were at- 
 tacked on return 75552000 24 
 
 Children who were not 
 attacked on return.. 20 29 86 87 126 74 18 21 8 469 
 
 The rapidly diminishing infectivity of the disease is 
 plainly shown by these figures. It is well known that 
 the specific bacilli not rarely disappear from cases of 
 diphtheria within a week or ten days of the onset of 
 the disease. In my own city only 1.8 per cent of the 
 cases retain their infection for ten weeks or more. The 
 various data that have been presented concerning scar- 
 let fever indicate that the infectivity of this disease 
 also disappears in much the same way, as does that of 
 diphtheria. Barlow (6) and Zilgien (7) have recently 
 considered this subject, and believe that in view of all 
 the facts, we are justified in assuming that in a large 
 number of mild cases of scarlet fever, the infectivity 
 disappears by the end of the third week. 
 
 Unfortunately we have no means of determining in 
 this disease as we have in diphtheria, the cases in 
 which this happens. An arbitrary time limit has to 
 
16 THE MODE OF INFECTION AND DUEATION OF 
 
 be fixed for the minimum period of isolation in scarlet 
 fever. In the majority of cities this is fixed at six 
 weeks, and in some English cities at seven or eight 
 weeks, but in certain American cities it is much less. 
 Thus it is, or was for many years, five weeks in Eoches- 
 ter, four weeks in Brookline, Mass., Concord, N. H., 
 Newton, Mass., Kansas City and Omaha, and three weeks 
 in Buffalo, Cambridge, Grand Rapids, Holyoke, Lowell, 
 Minneapolis, Newark, New York City, Syracuse and 
 Utica. Scarlet fever is even more prevalent in English 
 cities than it is in the cities of the United States, and 
 a study of the disease in the latter country does not in- 
 dicate that the cities which maintain a longer period 
 of isolation have an appreciably less amount of disease 
 than do those with a shorter period. In Providence 
 the period of isolation was shortened from five to four 
 weeks without noticeable change in the prevalence of 
 the disease. It is indeed true that nearly always the 
 minimum period of isolation is exceeded if desquama- 
 tion continues, but as will be seen, it is probable that 
 the exfoliated epidermis is not infectious. It is fair to 
 infer from these facts that the infectivity of scarlet 
 fever in its later stages is not very great. 
 
 It is certain however that a small number of cases 
 remain infectious for a very long time, just as some 
 cases of diphtheria may remain carriers of the bacilli 
 for many weeks or months, and it seems probable that 
 this late infectivity in scarlet fever is somewhat more 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 17 
 
 prolonged and frequent than it is in diphtheria. This 
 subject may best be studied in connection with cases 
 which carry home infection from the isolation hospital. 
 The English data are much the most valuable for this 
 purpose as the hospitalization of patients is carried 
 further there than in other countries, and the subject 
 has been more carefully studied. Three repoi'ts have 
 been made concerning these "return outbreaks" of 
 scarlet fever and diphtheria in the London hospitals, 
 covering the years 1899 to 1904. The number of 
 scarlet fever cases discharged from the hospitals during 
 this period was 57,810, and the number of " infecting 
 cases " i. e. cases which carried infection home from 
 the hospital was 2,225, or 3.8 per cent. It has been 
 argued that a good many of the apparent instances of 
 "return infection" are merely coincidences, but 
 Turner (8) has shown that this can be true of only a very 
 small number. Turner has presented his facts in the 
 form of diagrams which are well worth studying. 
 These diagrams show the time distribution of the cases 
 which develop after the return of the infecting case, 
 and it appears highly improbable that more than a 
 very few can be coincidences, or due to a lingering in- 
 fection in members of the family remaining at home, 
 or in the house itself. Such a large series of cases 
 gives an excellent opportunity for studying the dura- 
 tion and mode of infection in this disease. 
 
18 
 
 THE MODE OF INFECTION AND DURATION OP 
 
 The following table taken from Cameron's (9) report 
 shows the time of detention in certain hospitals of all 
 cases of scarlet fever treated in them, and also the 
 time of detention of the infecting cases, that is of the 
 cases which carried the infection to their homes. 
 
 TABLE m. 
 
 (August, J 90}, to July, 1902, indusivc.) 
 
 
 
 -4 
 
 -6 
 
 -8 
 
 -10 
 
 -12 
 
 -14 
 
 -16 
 
 to 
 
 'c3 
 
 
 g^ 
 
 
 
 
 
 
 
 
 O 
 
 g 
 
 "Infecting 
 
 
 
 
 
 
 
 
 
 
 
 Cases ". . . 
 
 
 3 
 
 41 
 
 209 
 
 210 
 
 112 
 
 34 
 
 24 
 
 20 
 
 653 
 
 Percentage . 
 
 
 .45 
 
 6.27 
 
 32.06 
 
 32.15 
 
 17.13 
 
 5.20 
 
 3.67 
 6. 
 
 3.06 
 73 
 
 
 "All Cases" 
 
 15 
 
 88 
 
 975 
 
 5,070 
 
 4,667 
 
 2,258 
 
 1,222 
 
 12 
 
 06 
 
 15.501 
 
 Percentage . 
 
 .09 
 
 .56 
 
 6.28 
 
 32.70 
 
 30.10 
 
 14.56 
 
 7.88 
 
 7. 
 
 78 
 
 
 This table shows that in 609 instances the infectivity 
 was prolonged beyond 6 weeks, in 190 instances 
 beyond 10 weeks, in 44 instances beyond 14 weeks and 
 in 20 instances beyond 16 weeks. A similar prolonga- 
 tion of infection is also shown by the tabulation of the 
 1,085 infectious cases in Turner's (10) report which is 
 shown on the following page: 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 
 
 19 
 
 TABLE IV. 
 
 Period of detention of infecting cases (primary Scarlet Fever only). 
 
 Detention in dats. 
 
 1902. 
 
 1903. 
 
 1904. 
 
 Total. 
 
 14 to 20 
 
 2 
 
 3 
 
 4 
 
 18 
 
 82 
 
 96 
 
 83 
 
 68 
 
 46 
 
 35 
 
 14 
 
 11 
 
 2 
 
 10 
 
 3 
 
 1 
 
 3 
 
 3 
 
 
 
 2 
 
 21 
 
 2 
 11 
 
 18 
 
 57 
 
 62 
 
 48 
 
 45 
 
 30 
 
 25 
 
 16 
 
 13 
 
 7 
 
 4 
 
 5 
 
 2 
 
 2 
 
 1 
 
 1 
 
 4 
 
 13 
 
 41 
 
 58 
 
 44 
 
 26 
 
 13 
 
 11 
 
 7 
 
 14 
 
 4 
 
 3 
 
 3 
 
 4 
 
 1 
 
 6 
 
 28 
 
 19 
 
 35 
 
 49 
 
 42 
 
 180 
 
 49 
 
 216 
 
 56 
 
 175 
 
 63 
 
 139 
 
 70 
 
 89 
 
 77 
 
 71 
 
 84 
 
 37 
 
 91 
 
 38 
 
 98 
 
 13 
 
 105 
 
 17 
 
 112 
 
 11 
 
 119 
 
 7 
 
 126 
 
 5 
 
 133 
 
 5 
 
 140 
 
 
 147 
 
 
 1 
 
 1 
 
 "'i' 
 
 1 
 
 154 
 
 
 1 
 
 161 
 
 2 
 
 1 
 
 3 
 
 168-175 
 
 1 
 
 
 
 
 
 
 486 
 
 350 
 
 249 
 
 1,085 
 
 
 Period of detention uncertain, two or 
 more infecting cases having Ibeen dis- 
 charged after different periods of deten- 
 
 16 
 
 20 
 
 11 
 
 47 
 
 
 
 Totals 
 
 502 
 
 370 
 
 260 
 
 1,132 
 
 
 The longest period noted by Turner was over 24 
 weeks. Instances of prolonged infectivity in scarlet 
 fever may occasionally be found in medical literature. 
 A number are reported by Newsholme (11). Other are 
 given by Cameron (12) in one of which the infectivity 
 
20 THE MODE OF INFECTION AND DURATION OF 
 
 lasted over 16 weeks, or 10 weeks after discharge from 
 the hospital. Zilgien (7) reports an instance where a 
 girl probably remained infectious from July 6 until the 
 following March. Simpson (13) gives several instances 
 of prolonged infectivity, one of them extending over 
 240 days, or 8 months. Most of these cases of long 
 standing infection have some discharge from nose or 
 ear. I have seen a case of scarlet fever which was 
 taken sick on June 25, and was discharged from the 
 hospital on November 15, apparently giving rise to two 
 other cases within a few days. This case had a dis- 
 charge from the ear. Such very prolonged infectivity 
 is apparently not very common. The 20 cases reported 
 by Turner as lasting over 16 weeks were only 3 per 
 cent of 653 infecting cases discharged from the hospital, 
 and only 0.12 per cent of the whole 15,501, cases 
 discharged. 
 
 It will also be seen from the tables that the patients 
 who remain in the hospital from 8 to 12 weeks furnish 
 the largest number of return cases. From this fact, as 
 well as from other considerations, Simpson, as well as 
 various other writers, have argued that infectivity is 
 increased by prolonged residence in a hospital, because 
 the patients absorb the scarlet fever virus, perhaps in 
 more virulent form, from other patients in the ward. 
 Both Cameron and Turner hold that this is probably 
 not so. One reason why patients detained over 8 
 weeks are more likely to prove infective, is because 
 
THE IKFBCTIOUS PERIOD IN SCARLET FEVER. 21 
 
 they are usually retained on account of some complica- 
 tion, which indicates a probably great virulence of the 
 disease poison. Complicating discharge from nose and 
 ear directly maintain inf ectivity. The figures also sho^ 
 that the longer these complicated cases are kept in the 
 hospital, so that opportunity may be afforded for com- 
 plete recovery, the fewer are the resulting return 
 cases, which could not be if infectivity were caused by 
 long residence in the hospital. That the duration of 
 infection depends on the type of the disease, virulence 
 of the virus, and the complications, and not on hos- 
 pitalization is also urged by Newsholme. The height- 
 ened virulence of the infecting cases, is shown by the 
 fact, as set forth by Cameron, (14) that the case fatality 
 of the return cases caused by them is 5.8 as compared 
 with 3.6 of all cases. 
 
 If cases are treated at home late recurrence of the 
 disease is noted there also. Thus in Providence, after 
 disinfection, there is a recurrence of the disease in the 
 same families in about 1.2 per cent of the families, and 
 in other families in the house in 2.4 per cent of the 
 families. Disinfection is usually done at the fifth or 
 sixth week. So also when well children are sent away 
 from home they will sometimes contract the disease on 
 their return, and as shown on page 15 the danger 
 decreases rapidly. Of 1,671 susceptible persons mostly 
 children so removed and returned after the termination 
 
22 THE MODE OF INFECTION AND DURATION OF 
 
 of isolation, usually about the fifth or sixth week, 31 
 or 1.2 per cent have been taken sick with the disease. 
 
 The tables show also, particularly those of Turner, 
 that the cases discharged before 6 weeks have a lower 
 infectivity than those discharged later. These early 
 cases are mild and uncomplicated, and apparently lose 
 their infecting power before the others. 
 
 Some are beginning to think that the period of 
 isolation for scarlet fever has been unduly prolonged, 
 at least in England, and, as will be shown later, the 
 average period of detention in the hospital, has in 
 several towns been materially reduced without causing 
 any increase in the number of return cases. Barlow 
 (16) thinks that many mild cases are infectious but a 
 few days. Zilgien (17) agrees with Barlow and gives 
 instances where isolation during the sore throat only, 
 proved sufficient. 
 
 From a consideration of the facts here presented it 
 appears that cases of scarlet fever are infectious from the 
 very beginning, that the period of greatest infectivity 
 is probably during the presence of the acute symptoms, 
 sore throat, fever and rash, that it probably diminishes 
 rather rapidly after the disappearance of these symp- 
 toms, and that by the end of four weeks has disap- 
 peared from all but a small percentage of the cases. 
 That in some instances infectivity may persist for 
 many weeks and even for several months. 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 23 
 
 SOURCES OF THE INFECTION IN THE BODY. 
 
 It is now necessary to consider the source of the 
 virus in the human body in order that we may the 
 better determine the conditions under which individual 
 patients are infective. 
 
 The Throat. There is much reason for thinking 
 that the specific poison of scarlet fever is contained in 
 the secretions of the throat in the early stages of the 
 disease, and perhaps it may persist there, in some at 
 least, of the cases of long continued infection. The 
 pathological process is most acute and marked in the 
 throat, and the contagiousness of the disease is great- 
 est during the acute stages and rapidly diminishes with 
 the abatement of the throat symptoms. There are 
 also a few direct observations which are in accord with 
 this view. Jurgensen (15) says that Copland reports a 
 case infected by the sputum in the early stages of the 
 disease. Stickler (16) inoculated into 10 children mucus 
 taken from the throat of a patient just after the rash 
 appeared. Every child developed within from 12 to 
 72 hours a fair picture of scarlet fever. Griinbaum 
 (17) reports a single instance of the possible infection 
 of an ape with the secretion from the throat of a 
 scarlet fever patient. Cameron (18) shows in the 
 accompanying table that while morbid conditions of 
 the throat, such as enlarged tonsils, and inflammation 
 with excessive secretion, were reported from only 6.3 
 
24 
 
 THE MODE OP INFECTION AND DURATION OF 
 
 § 
 
 CQ 
 
 S 
 
 
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 12 
 19.2 
 
 12,8 
 
 77. 
 
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 P- 
 
 
 Ph 
 
THE INFECTIOUS PERIOD IN SCARLET EEVEE. 25 
 
 per cent of the total scarlet fever cases discharged from 
 the hospital, such conditions were associated with 
 32.25 per cent of the infecting cases. Scarlet fever 
 sine eruptione, that is with the symptoms confined ex- 
 clusively to the mucus surfaces, chiefly the throat, are 
 reported by all writers on this disease. It is the in- 
 fectivity of these cases which establishes the diagnosis, 
 and the fact that they are infectious, though throat 
 symptoms only are apparent, strengthens the conclu- 
 sion that the throat is the seat of infection. Cameron 
 (19) reports 104 cases of possible scarlet fever sore 
 throats many of which proved infectious. A milk 
 outbreak with many such cases is described by News- 
 holme (20). 
 
 In the JSfose. In diphtheria the specific bacillus is 
 found rather more often in the nose than in the throat, 
 so we would expect that in scarlet fever, the nose as 
 well as the throat, might be infected. Nasal discharge 
 may be observed at any stage of the disease, but it is 
 only in the later stages that its infectivity seems to be 
 established. The middle ear trouble which is so fre- 
 quent a complication of scarlet fever, is doubtless due 
 to an extension of the pathological process from the 
 naso-pharynx, A similar extension takes place in 
 diphtheria, much more commonly than is usually stated. 
 That some form of rhinitis, usually virulent, is fre- 
 quently associated with prolonged infectivity, has been 
 
Ii6 THE MODE OP INFECTION AND DURATION OP 
 
 noted by a number of English observers as Newsholme, 
 Pugh, Niven, Lauder, Simpson, Cameron and Turner, 
 and is well shown by Cameron's table shown on page 
 24. He shows that of the infecting cases dis- 
 charged from the hospital 52.31 per cent had some 
 form of rhinitis, while of the total cases only 3.56 per 
 cent had this complication. 
 
 It is observed that nasal, and also aural discharge, 
 in convalescent scarlet fever patients, is not contin- 
 uous, but that often a number of days or weeks elapse 
 in which there is no discharge. A renewal of the dis- 
 charge from the nose is sometimes accompanied by a 
 recrudesence of infectivity, shown by the patient 
 transmitting the disease to another. Thus Cameron 
 (21) reports a case which was discharged well from the 
 hospital, but 22 days later a rhinitis developed, and 
 another case in the family was taken sick in 5 days. 
 Cameron gives a score or more of such cases. 
 
 Besides the fact that a persistent sore throat and 
 an excessive nasal discharge are found to a considerable 
 excess in infecting cases, and that recrudesence of 
 these symptoms is followed by the development of 
 fresh cases, evidence of the infective nature of these 
 discharges is found in the decrease in the number of 
 return cases where special care has been taken not to 
 send home patients in which throat and nose symp- 
 toms are present. In many of the English hospitals 
 less attention is being paid to desquamation and more 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 27 
 
 to the condition of the nose and pharynx. The result 
 is that in London, Birmingham, Manchester, South- 
 ampton, Huddersfield, and other places the number of 
 return cases is diminishing, and at the same time the 
 period of detention in the hospital has been materially 
 shortened. 
 
 The Ear. A discharging ear in a convalescent 
 scarlet fever patient has long been believed to be in- 
 fectious, and is still considered so by most observers. 
 Cameron (22) thinks it is not proved that otorrhea is 
 infectious, and he suspects that it is not. Of 123 
 patients with otorrhea, only 8 caused the infection of 
 others, and in all of these there existed a concurrent 
 rhinitis. Nevertheless he shows, p. 24, that while 
 only 2.16 per cent of all discharged scarlet fever cases 
 have otorrhea, at the time of discharge, 8.33 per cent 
 of the infecting cases had it. Otorrhea frequently 
 occurs in diphtheria, and I have repeatedly found the 
 diphtheria bacillus in the discharge, as have others. 
 We should expect also to find the discharge infectious 
 in scarlet fever, and it does not appear on present 
 evidence to be safe to consider it otherwise. An 
 otorrhea may last a very long time, but the discharge 
 is often very slight, and in many instances it is not 
 necessary to isolate the patient if the ear is properly 
 cared for, and perhaps kept plugged with cotton. 
 
28 THE MODE OF INFECTION AND DURATION OF 
 
 The Skin. From time immemorial the desquamat- 
 ing skin of scarlet has been considered not merely in- 
 fectious, but even as the sole vehicle of infection. It 
 is not surprising that this view should have arisen, 
 for the desquamation of smallpox was demonstrated by 
 inoculation to be infectious, and that of scarlet fever 
 was by analogy assumed to be so. Desquamation per- 
 sists a long time, as does the infectivity, and the two 
 often disappear together. Formerly the air was be- 
 lieved to be the chief carrier of infection, and what 
 could be more readily carried by the air than the light 
 and fine epidermal scales ? But of late years many 
 have begun to question the infectivity of the ex- 
 fohated epidermis. Among these may be mentioned 
 Boobbyer (23), Richards (24), Gilbert (25), Millard (26), 
 Lauder (27), Cameron (28), Bond (29), Moore (30), 
 Turner (31), and Lemoine (32). 
 
 It is recognized that the assumed analogy between 
 scarlet fever and smallpox is a false one, and that 
 scarlet fever quite closely resembles diphtheria. It 
 seems probable that the pathological process is for the 
 most part confined to the mucous surfaces, chiefly of 
 the throat and nose, and that the exantham, and sub- 
 sequent desquamation, are due to toxins elaborated for 
 the most part in the throat. The a priori argument is 
 against the infectiousness of the exfoliated skin. As 
 for direct evidence of such infectiousness there is none. 
 The burden of proof lies upon those who assert the 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 29 
 
 affirmative. On the other hand there is positive and 
 strong evidenee that desquamation is not always dan- 
 gerous. There is a considerable mass of evidence, 
 mostly from English hospital experience, which shows 
 that in the discharge of scarlet fever cases, desquama- 
 tion may be neglected. Priestly (33) during a small 
 pox outbreak at Leicester discharged 120 scarlet 
 fever patients who were desquamating, and no second- 
 ary cases developed in any of the homes. Lauder at 
 Southampton (34) sent out 204 desquamating patients 
 only 2 of which, 0.98 per cent, gave rise to secondary 
 cases. One of these infecting cases also had nasal dis- 
 charge. Of the 121 cases without desquamation dis- 
 charged during the same period 5, or 4.13 per cent 
 proved infective, all of which had some abnormal dis- 
 charge from nose, throat, or ear. By paying particular 
 attention to the mucous surfaces while neglecting des- 
 quamation, Lauder was able to reduce the percentage 
 of return cases from 4.27 in 1902 to 2.15 in 1903, at 
 the same time shortening the period of detention in 
 the hospital from 48 to 34 days. 
 
 In certain of the London hospitals, 1902-4, no case 
 was discharged while desquamating, and of 6,164 dis- 
 charges, 246 or 3.99 per cent were followed by return 
 cases. Of 12,000 cases discharged from hospitals where 
 no attention was paid to desquamation, and many of 
 which cases were desquamating, return cases developed 
 269 times, or 2.24 per cent. Undoubtedly the hos- 
 
30 THE MODE OF INFECTION AND DUEATION OF 
 
 pitals which paid little attention to desquamation paid 
 special attention to mucous discharges and hence the 
 lower number of return cases. 
 
 Urine, Feces, Pits from Glands. There seems to 
 be no evidence either for or against the infectiousness 
 of these excretions. 
 
 Infectivity with No Apparent Pathological Condition. 
 That convalescents from scarlet fever should carry 
 the virus of the disease while exhibiting no symptoms 
 or lesions, is not surprising. It is a phenomenon 
 common to many diseases, and has been particularly 
 studied in diphtheria and typhoid fever. The " carrier 
 case " is coming to be recognized as a most important, 
 if not the most important, factor in the spread of these 
 two diseases. As the specific germ of scarlet fever is 
 unknown, the evidence of the existence of "carriers" 
 of scarlet fever is not so conclusive or abundant as for 
 diphtheria and typhoid fever. Yet there is little doubt 
 that many persons are infected with scarlet fever and 
 capable of giving the disease to others, and yet pre- 
 sent no symptoms whatever of disease. Thus 125 of 
 the infecting cases discharged from the London hospi- 
 tals and investigated by Cameron (18) showed no ap- 
 parent abnormal condition. Millard (35) showed that 
 58.2 per cent of the infecting cases at Birmingham 
 were quite clear in every way, and Boobbyer states 
 that 11 of 26 infecting cases at Nottingham were free 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 31 
 
 from symptoms of disease. I have kept no record of 
 the condition of the infecting cases observed by me, 
 whether discharged from the hospital, or remaining in 
 their homes, but it may be definitely stated that very 
 many of these showed no discharge from nose or ear, 
 no sore throat, no desquamation, and in fact no other 
 symptoms of the disease. Cameron reports 30 in- 
 stances, and Turner 44, in which diphtheria patients 
 carried scarlet fever from the hospital to their homes. 
 The presence of scarlet fever infection in these cases 
 had not been indicated by any physical signs. There 
 is a good deal of evidence that perfectly well persons, 
 who have never had scarlet fever, may nevertheless 
 carry the poison in their persons and transmit it to 
 others, but in the absence of bacteriological evidence 
 we have no means of knowing how long such infection 
 may last. 
 
 MODES OF INFECTION. 
 
 Before proceeding to consider the different modes 
 of infection in scarlet fever we may inquire what is 
 known as to the degree of contagiousness of this dis- 
 ease. I have prepared the following table to show it's 
 infectivity in families in which the patient lives and 
 is kept at home during the whole course of the disease. 
 
32 
 
 THE MODE OF INFECTION AND DURATION OF 
 
 TABLE VL SCARLET FEVER. 
 
 C a.ses from families in which the patient lived and remained at home during 
 
 the whole illness. 
 
 Age and Sex of Primary and Secondary Cases. 
 
 Primary Cases. 
 
 Ages. 
 
 Under 1 yr 
 1 
 
 10. 
 11. 
 12. 
 13. 
 14. 
 15. 
 16. 
 17. 
 18. 
 19. 
 20. 
 A.. 
 
 M. 
 
 is 
 
 < 
 
 F. 
 
 II 
 
 15 
 
 10.9 
 
 6 
 
 4.3 
 
 28 
 
 22.0 
 
 30 
 
 22.6 
 
 61 
 
 35.1 
 
 55 
 
 39.6 
 
 66 
 
 39.1 
 
 83 
 
 45.9 
 
 75 
 
 39.1 
 
 69 
 
 39.4 
 
 74 
 
 38.5 
 
 77 
 
 45.0 
 
 83 
 
 46.8 
 
 91 
 
 45.5 
 
 69 
 
 43.9 
 
 84 
 
 45.2 
 
 62 
 
 40.8 
 
 86 
 
 47.5 
 
 52 
 
 40.0 
 
 75 
 
 43.9 
 
 42 
 
 29.4 
 
 54 
 
 38.6 
 
 32 
 
 25.8 
 
 48 
 
 39.7 
 
 21 
 
 20.4 
 
 36 
 
 33.3 
 
 11 
 
 15.9 
 
 25 
 
 25.3 
 
 24 
 
 26.7 
 
 22 
 
 26.2 
 
 11 
 
 15.7 
 
 15 
 
 19.5 
 
 10 
 
 13.0 
 
 10 
 
 14.9 
 
 7 
 
 10.2 
 
 6 
 
 11.3 
 
 5 
 
 8.8 
 
 8 
 
 13.6 
 
 5 
 
 9.6 
 
 5 
 
 9.8 
 
 3 
 
 6.8 
 
 3 
 
 7.0 
 
 56 
 
 3.1 
 
 63 
 
 3.1 
 
 812 
 
 18.8 
 
 951 
 
 20.7 
 
 Is 
 
 21 
 
 58 
 
 116 
 
 149 
 
 144 
 
 151 
 
 174 
 
 153 
 
 148 
 
 127 
 
 96 
 
 80 
 
 57 
 
 36 
 
 46 
 
 26 
 
 20 
 
 13 
 
 13 
 
 10 
 
 6 
 
 119 
 
 
 7.6 
 22.3 
 37.1 
 42.6 
 39.6 
 41.6 
 45.7 
 44.6 
 44.4 
 42.2 
 33.9 
 32.7 
 27.0 
 21.4 
 26.4 
 17.7 
 13.9 
 10 
 11 
 
 9 
 
 1,763 19.8 
 
 Secondabt Oases. 
 
 M. 
 
 16 
 
 32 
 
 40 
 
 41 
 
 37 
 
 30 
 
 22 
 
 28 
 
 12 
 
 18 
 
 8 
 
 13 
 
 6 
 
 2 
 
 3 
 
 2 
 
 5 
 
 2 
 
 2 
 
 
 
 13 
 
 
 4.9 
 16.2 
 28.3 
 38.8 
 86.3 
 31.4 
 30.6 
 25.0 
 31.1 
 15.4 
 17.8 
 
 8.7 
 15.9 
 10.3 
 
 3 
 
 5 
 
 S.O 
 8.1 
 3.8 
 4.8 
 .0 
 .7 
 
 338 9.6 
 
 7 
 
 24 
 
 17 
 
 21 
 
 37 
 
 31 
 
 32 
 
 30 
 
 30 
 
 24 
 
 18 
 
 16 
 
 16 
 
 5 
 
 10 
 
 9 
 
 6 
 
 2 
 
 q 
 
 2 
 
 2 
 
 34 
 
 376 
 
 
 5.2 
 23.3 
 20.2 
 21.4 
 34.9 
 33.0 
 29.3 
 29.4 
 31.6 
 25.0 
 20.9 
 21.9 
 22.2 
 
 6.8 
 16.] 
 14.5 
 10.5 
 
 4.3 
 
 5. 
 
 4.2 
 
 5.0 
 
 1.7 
 
 10.3 
 
 
 13 
 
 40 
 
 49 
 
 61 
 
 78 
 
 68 
 
 62 
 
 52 
 
 58 
 
 36 
 
 36 
 
 24 
 
 29 
 
 11 
 
 12 
 
 12 
 
 8 
 
 7 
 
 5 
 
 4 
 
 2 
 
 47 
 
 714 
 
 <! 
 
 5.1 
 
 19.8 
 
 24.9 
 
 30.3 
 
 35.6 
 
 32.1 
 
 30.0 
 
 27.4 
 
 31.4 
 
 20.7 
 
 19.3 
 
 14.5 
 
 18.8 
 
 8.3 
 
 9.4 
 
 9.9 
 
 6.5 
 
 6.4 
 
 4.8 
 
 4.2 
 
 2.5 
 
 1.3 
 
 10.0 
 
THE INFECTIOUS PERIOD IN SCARLET FEVEU, 33 
 
 While it is most important to know to what degree 
 scarlet fever may be expected to spread through the 
 family, it is of more importance from an epidemiologi- 
 cal point of view to know what the chance is of its 
 spreading from family to family, and in schools and 
 similar places. Instances are not rare where children 
 presumably in the infectious stage of scarlet fever, 
 have mingled freely with others for many days, or 
 perhaps weeks, with little or no extension of the dis- 
 ease. I have notes of an instance where a boy with 
 scarlet fever in the sore throat stage, attended a Sun- 
 day School festival, and no other case developed 
 among the large number of children present. At an 
 infant asylum a child was sick with mild scarlet fever 
 for 17 days, mingling freely with about 75 children, 
 mostly under 5 years of age, and only 3 other cases 
 resulted. At a large school, a girl returned at the end 
 of the first week of an attack of scarlet fever, and con- 
 tinned her attendance for 20 days. Only 3 or 4 cases 
 developed in that school. Similar and even more 
 marked instances of apparently feeble infectivity are 
 reported by others, and the same phenomenon has 
 been noted in smallpox and diphtheria. In the latter 
 disease bacteriology has shown us that it is quite com- 
 mon for "carriers" to mingle freely with others with- 
 out spreading the disease. I have known of a teacher 
 with virulent diphtheria bacilli in her throat from the 
 
34 THE MODE OF INFECTION AND DURATION OF 
 
 first of January to the middle of April, who taught in 
 a kindergarten all that time, but who did not transmit 
 the disease to any one. Hence we should not be sur- 
 prised to find that scarlet fever, except under condi- 
 tions of the closest contact, does not show a very high 
 degree of contagiousness. 
 
 In Providence most people live in tenement houses 
 with one or more other families, and the amount of 
 infection of second families in the house, and the con- 
 ditions under which this takes place is of much epi- 
 demiological interest. I have records of such an ex- 
 tension of the disease for a number of years. Of 4033 
 other families living in the same house with the family 
 first attacked, and using the same doors and passage- 
 ways, 291 or 7.2 per cent have been invaded. This is 
 a surprisingly small percentage, when it is remembered 
 that most of the families are poor, or at least in 
 moderate circumstances, and that the houses are fre- 
 quently very much crowded, and the people often 
 ignorant. and careless. Observation has shown that a 
 large part of the infection takes place before the dis- 
 ease is recognized, and while there is a free mingling 
 of the children and perhaps other members of the 
 families, and a certain other part of the cases are due 
 to a mingling after the termination of isolation, when 
 it is supposed that the infective stage is passed. But 
 as we have seen the infective stage in a small percen- 
 tage of cases continues unrecognized, and often un- 
 
THE INFECTIOUS PBKIOD IN SCARLET FEVEK. 35 
 
 recognizable for a long time. The time at which in- 
 fection of second families takes place is shown by the 
 table on page 13 which, however, only covers the 
 five years during which these special data have been 
 tabulated. Of 80 families which developed the disease 
 while the warning sign was on the house 54 were dur- 
 ing the first two weeks of the initial sickness. Most of 
 these cases probably contracted the disease before the 
 house was placarded. From the end of the second 
 week of the disease in the first family to the end of 
 the second month, there were only 24 instances in 
 which there was extension of the disease from one 
 family to another in the same house. This is only 
 1.3 per cent of the 1,888 families exposed. 
 
 It appears then that scarlet fever almost never ex- 
 tends from one family to another in the same house, 
 except when there is free communication between the 
 members, usually before the disease is recognized, 
 more rarely after the termination of isolation, and 
 more rarely still while the warning sign is upon the 
 house. This happens in houses where two, and per- 
 haps four or six families, use the same hallways, doors, 
 cellars and perhaps the same water closets. The 
 woodwork in these houses is rarely cleaned, and the 
 children and grown people in the infected family, even 
 the mother who nurses the patient, are constantly run- 
 ning their hands up and down the stair-rail, along the 
 walls, and are opening and closing the doors. The 
 
36 THE MODE OF INFECTION AND DURATION OF 
 
 mother will carry slops to the cellar, and the garbage 
 and refuse to the yard. That the disease does not 
 spread under these conditions throws light on the 
 degree of infectivity and the mode of infection in this 
 disease. 
 
 Among the modes of infection worthy of considera- 
 tion are the following : 
 
 Infectio7i hy Contact. This is the most obvious 
 means by which the extension of the disease may take 
 place. The term is coming into quite general use but 
 is not accurately defined. In this connection it means 
 the quite direct transference, of quite fresh infective 
 material. The transference may be immediate, as in 
 kissing, or far more often, mediate, as by two persons 
 drinking from the same glass, or moistening the same 
 pencil in the mouth. There are a thousand and one 
 ways in which young children thus transfer the secre- 
 tions of the mouth and nose from one to another. 
 They are constantly putting their fingers and every 
 imaginable article, into the mouth, or are boring the nose 
 with the fingers. Toys, cups, spoons, pencils, candy, 
 food, string and countless other things, may thus easily 
 become the bearers of the secretions from child to child, 
 and there is often likely to be an even more direct 
 transfer as they romp and tumble over each other in 
 play. The opportunities for such contact infection in 
 the family are so numerous and constant that the won- 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 37 
 
 der is not that infection takes place, but that half of 
 the children of even the most susceptible age escape 
 during the month or six weeks' presence of scarlet 
 fever. It is not improbable that apparent differences 
 in age and sex "susceptibility" to the disease, may be 
 largely an expression of the chance for contact with 
 the patient. Infants are less susceptible perhaps be- 
 cause they do not mingle freely with and play with 
 other children. The years of greatest susceptibility, 
 from two to ten are exactly those years in which chil- 
 dren are careless and have little idea of cleanliness, 
 and are constantly coming into the closest possible 
 contact with one another. A noticeable feature of 
 family infection is that women over 16 years of age 
 are more than twice as likely to contract scarlet fever 
 when it has once invaded the family, than are men of 
 the same ages, a fact to be explained perhaps by the 
 women coming into far more intimate personal contact 
 with the patient than do the men. The constant 
 escape from the disease of the vast majority of other 
 families in the same house, speaks for the necessity of 
 quite close contact to insure infection. This view that 
 contact infection is the chief mode of transference of 
 scarlet fever is coming to be recognized by many of 
 the most careful observers, especially in England and 
 France. Thus Cameron (12) gives several instances in 
 which the development of return cases did not take 
 place as long as the infecting case did not come into 
 
38 THE MODE OF INFECTION AND DURATION OF 
 
 immediate contact with susceptible members of the 
 family. Niven in Manchester fi'om a study of return 
 cases in that city is convinced that if the children can be 
 kept slightly apart in the family, there is no transfer- 
 ence of the disease. That there is much good evidence 
 that scarlet fever does not spread in the absence of 
 contact will be shown when considering the possibility 
 of infection by air. 
 
 Doubtless the chief reason for scepticism as to the 
 sufficiency of contact infection to account for the ex- 
 tension of scarlet fever, is the fact that in a large pro- 
 portion of cases it is impossible to find any connection 
 with a previous case. If there is no change for contact 
 infection from another case, it seems to be necessary 
 to discover some other and more circuitous, or less vis- 
 ible, mode of transference. This point of view depends 
 upon the assumption that all or nearly all persons 
 infected with scarlet fever are recognized as such. 
 This assumption at the present day is entirely unwar- 
 ranted. It is now well known that in many of the in- 
 fectious diseases, atypical forms, not easily recognized 
 clinically and frequently not seen by a physician, are 
 very numerous, perhaps more numerous than are the 
 cases seen and recognized by medical men. This is 
 noticeably true of diphtheria, typhoid fever and yellow 
 fever. It has also, within a few years, been learned, 
 what was never before suspected, that in many diseases 
 an even larger number of persons are the " carriers " 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 39 
 
 of disease germs without exhibiting any symptoms of 
 disease. This has been proved true of diphtheria, 
 typhoid fever, malaria and particularly of cerebro-spi- 
 nal-meningitis. 
 
 Unfortunately the laboratory cannot as yet help us 
 in findino: the " missed cases " and '• carriers " of scarlet 
 fever. But all who have made a careful study of this 
 disease know that there are very frequently seen cases 
 with a scarcely discernible indefinite rash, lasting for 
 only a few hours, a rise in temperature of only a degree 
 or two, lasting also only a few hours, and the merest 
 trace of sore throat. Sometimes the rash may be 
 entirely absent. In institutions and families, such 
 cases, considered doubtful at first, or perhaps neglected, 
 prove to be the origin of typical symptoms in others. 
 They are the missed cases which are such a factor in 
 the maintenance of this disease. There are many 
 references to them in the reports of health officers and 
 in medical literature. Among others who report such 
 atypical cases are Newsholme (11), Gaziot (36), Welch 
 and Shamberg (37), and Cameron (38). In most of these 
 "missed" cases there were some slight symptoms, but 
 overlooked or misunderstood at the time. In Manchester 
 in 1906 there were discovered 229 missed cases, mostly 
 of a mild character. From these 139 other cases had 
 developed (39). True " carriers," that is perfectly 
 well persons, are sometimes reported. Thus I saw an 
 instance where a woman apparently so carried scarlet 
 
40 THE MODE OF INFECTION AND DURATION OF 
 
 fever to her child. She had been taking care of 
 another child, and after an entire change of clothing, 
 bath and shampoo, visited the first named child who 
 was taken sick two days later. Newsholme reports 
 what he thinks are possibly, or even probably, similar 
 cases. Newman (40), of Finsbury, (London) noted 
 five carriers among school children, three of whom, 
 though they had never had the disease, transmitted it 
 to others. Cameron (41) reports many such cases. 
 While the proof of the number of carriers and missed 
 cases is not so conclusive as it is for diphtheria and 
 typhoid fever, and never can be in the absence of lab- 
 oratory evidence, it is yet sufficient to warrant the 
 belief that the unrecognized sources of infection are 
 numerous enough to permit the origin from them by 
 contact infection of all the recognized cases of the 
 disease. 
 
 Infection by Fomites. Whenever in the past it was 
 impossible to trace any direct connection between cases 
 of scarlet fever, indirect means of communication were 
 sought for, and it was not infrequently found that a 
 toy, book, clothing, or some other material thing, 
 which had previously been used by one scarlet fever 
 patient, was used by another case a short time before 
 the development of the disease. These supposed 
 bearers of infection are called fomites, and it has been 
 alleged that they can retain their virulence for many 
 
THE INFECTIOUS PERIOD IN SCAELET FEVER. 41 
 
 weeks, months and even years. It is seen that the 
 distinction between immediate contact and fomites in- 
 fection is not a sharp one. The common usage is to 
 apply the term contact infection when the interval in 
 time is short, perhaps a few hours, often only a few 
 minutes, and to use the word fomites when the interval 
 is long. In contact infection the infective material is 
 moist, or at least not dry, in the case of fomites, we 
 commonly think of the infective material as pretty 
 well dried. 
 
 It is unnecessary to give instances of alleged fomites 
 infection in this disease. They are found scattered 
 through medical literature in almost every article and 
 text book dealing with scarlet fever. In many of 
 them the disease is traced to an infected schoolroom 
 or house, or to clothing, books or toys which have been 
 carried long distances. Often no mention is made of 
 the occupants of the room, or the bearers of the goods, 
 who are much more likely to have been the " carriers " 
 of living germs, than the things were to bear even 
 dead germs, a fact which is rarely recognized by the 
 narrators. Often no pretence is made to exclude 
 other sources of infection, and in most instances there 
 is merely a possibility and not even a probability, that 
 the fomites were really the source of the disease. The 
 utter destruction by Reed, of the implicit confidence 
 formerly placed in the role played by fomites in the 
 spread of yellow fever, should make us wary of admit- 
 
42 THE MODE OF INFECTION AND DURATION OF 
 
 ting the much less convincing proofs of fomites infec- 
 tion in scarlet fever. Diphtheria also has long been 
 considered a fomites borne disease, but the entire 
 abandonment of disinfection after that disease, in 
 Providence (42) has not resulted in any increase in the 
 number of cases. There is certainly no stronger evi- 
 dence of infection by fomites in scarlet fever than 
 there was for diphtheria. Lemoine (43) has shown that 
 in the military hospital at Yal de Grace it was possible 
 to put a considerable number of persons in a ward just 
 cleared of scarlet fever patients and with no disinfec- 
 tion, and yet without any one contracting the disease. 
 At a recent conference (43) in Paris, Courmont, Comby 
 and others affirmed that the very thorough disinfection 
 of goods and houses carried on by the sanitary authori- 
 ties of that city is unnecessary, and has no effect in 
 diminishing the spread of scarlet fever, diphtheria or 
 measles. In England it has been claimed by some that 
 the alleged " return cases " of scarlet fever are not so 
 often due to the return of the patient, as to failure of 
 disinfection, but Cameron (44) has shown that this 
 cannot be true, for the cases are associated chiefly with 
 patients of certain ages, and particularly with those 
 suffering from complications. 
 
 Perhaps the best evidence that infection by fomites 
 is not easy, is found in the fact previously referred to, 
 that there is so little extension of the disease in tene- 
 ment houses. If the mothers, fathers, brothers and 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 43 
 
 sisters, of the patient, do not infect the hallways, stair 
 rails, doors and water closets so as to cause the disease 
 in the other inmates of the house, can there be any 
 appreciable danger of their carrying the virus in their 
 clothes to their work or play ? 
 
 It will not be denied that infection by fomites may 
 not take place in scarlet fever, nor that there may be 
 some instances of long persisting inf ectivity by fomites. 
 But it is affirmed that there is no evidence that 
 such a mode of infection plays any appreciable part in 
 the extension of the disease, and there is much e^ddence 
 that it does not. 
 
 Lifection hy Air. Another explanation of the 
 source of scarlet fever which cannot be traced to 
 direct contact with another case, is that the infection 
 is airborne. This idea of the importance of airborne 
 infection depends very largely on the belief that the 
 desquamating epidermis is infectious, a belief for 
 which it has been shown there is no evidence. The 
 writer like every health officer, has frequently noted 
 that a case of this disease may remain in school or 
 hospital ward for days, or sometimes for weeks, with- 
 out another case developing, or at most only one or 
 two cases. Such facts indicate that the disease is not 
 easily airborne. Visitors to fever hospitals do not 
 contract scarlet fever. Thus of 300 to 400 non- 
 immune students who ATsited the scarlet fever wards of 
 
44 THE MODE OF INFECTION AND DURATION OF 
 
 the Philadelphia hospital, remaining in the ward from 
 twenty minutes to an hour, not one contracted the 
 disease (46). Oftentimes scarlet fever does attack 
 other patients in hospitals but it is in a manner to in- 
 dicate contact rather than airborne infection. When 
 contact infection is rigidly guarded against as in the 
 Pasteur Hospital in Paris, scarlet fever may be and is 
 treated in the same ward with other diseases without 
 cross infection. 
 
 Attention has already been called to the compara- 
 tive rarity with which scarlet fever passes from one 
 family to another in the same house, and I have 
 shown that when it does so occur it is almost always 
 due to free communication between the families, that 
 is to contact infection. Notwithstanding the fact that 
 the doors of tenements are frequently opposite one 
 another and that during a considerable part of the 
 year the doors and windows are wide open, infection 
 by the air does not take place. 
 
 If scarlet fever is not airborne from family to family 
 in the house, one would not expect it to be borne 
 from house to house by the air. Yet such a claim is 
 sometimes made, that the virus of the disease may thus 
 be transmitted a considerable distance. A number of 
 the reports of the health department of Philadelphia 
 contain shaded maps to show the greater prevalence 
 of this disease, as well as of smallpox, in those parts 
 of the city near the hospital. I do not think that 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 45 
 
 much value attaches to such maps for there are too 
 many factors involved, and very rarely is the intensity 
 of the disease as great close to the hospital as the 
 theory demands. Moreover around very many hospi- 
 tals no such distribution of the disease can be shown. 
 Thus Tarnissier (46) in Paris found that Enfantes 
 Malades and Trousseau hospitals could not be con- 
 sidered foci of infection. The same is true of the 
 scarlet fever wards in Providence, in Detroit, and in 
 Boston. In the latter city (47) for the period studied 
 there Avere no cases of the disease within one eighth 
 of a mile of the hospital, while in the next eighth of a 
 mile circle there were 68 cases, in the next 71, in the 
 next 75, and in the next 72. 
 
 Where various contagious diseases are treated in 
 different wards of the same hospital there is sometimes 
 cross infection. But this occurs so irregularly as to 
 time and place, and is so limited in amount that it can 
 scarcely be attributed to anything but contact infec- 
 tion. As most of the physicians and nurses in our con- 
 tagious hospitals have no appreciation of what true 
 medical asepsis really means, it is surprising that we 
 see as little cross infection as we do. 
 
 Perhaps the best evidence we have that scarlet fever 
 is not airborne is that furnished by the Pasteur Hospi- 
 tal in Paris. In this hospital, patients with different 
 diseases are cared for in separate rooms opening out 
 of a common corridor. If air infection is dangerous 
 
46 THE MODE OF INFECTION AND DUKATION OF 
 
 anywhere it ought to be under these conditions. Be- 
 tween October 1, 1900, when the hospital was opened, 
 and April 19, 1903, 2,000 patients were received, of 
 whom 92 had scarlet fever, but in no instance did any 
 one in the hospital contract this disease (48). 
 
 There is no direct bacteriological evidence bearing 
 on the question of the aerial convection of the scarlet 
 fever virus. Yet bacteriology does offer some sugges- 
 tions. As the skin is probably not infectious, we must 
 look to the mucous surfaces for the source of our air- 
 borne infection, but the laboratory has shown us that 
 bacteria and other solid particles are not thrown off 
 from moist surfaces, but are rather entangled in them. 
 The only way that infection can pass from throat or 
 nose, is by means of the little droplets wlach are 
 thrown off in coughing, sneezing, and even m talking. 
 It has been shown that usually the droplets which are 
 large enough to infect, speedily sink, so that droplet 
 infection will rarely take place over a yard from the 
 patient. Droplet infection at short distances is doubt- 
 less possible in scarlet fever, and in this sense it is an 
 airborne disease. But for all practical purposes droplet 
 infection more nearly resembles contact infection than 
 it does aerial infection as the latter is generally under- 
 stood. 
 
 Infection hy Milk, It has long been known that 
 milk may be the means of spreading the virus of scar- 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 47 
 
 let fever, and a considerable number of outbreaks of 
 the disease have been traced to this source. A federal 
 report issued in 1908 (49), notes 51. such outbreaks, 
 but doubtless others have been reported which were 
 not included in this enumeration. This seems like a 
 serious indictment of milk, but when it is taken in con- 
 nection with the. vast number of cases of scarlet fever 
 that have occurred in Europe and America during the 
 last thirty or forty years, it will appear that milk 
 infection is not after all a very important factor in the 
 spread of this disease. Milk outbreaks of scarlet fever, 
 like milk outbreaks of other diseases, are characterized 
 by a sudden onset, and the occurrence of a large num- 
 ber of cases within a brief period. As the incubation 
 of scarlet fever is short, and the infection of the milk 
 is usually temporary, the cases are often massed in a 
 period of a few days only. Thus of the 717 cases in 
 the milk outbreak in Boston in 1907 (50), 485 occurred 
 within 6 days. The exceptionally explosive character 
 of these outbreaks renders it likely that few escape 
 notice, yet it appears that they are quite rarely re- 
 ported. Only one has come to the notice of the writer 
 during an experience of many years. In this outbreak 
 there were 26 cases, a very small part of the 13,001 
 cases which have come under his observation. 
 
 It matters little for our present purpose, how the 
 milk becomes infected. It has been claimed by some 
 that cows may have scarlet fever and infect the milk 
 
48 THE MODE OF INFECTION AND DTJEATION OF 
 
 directly. Klein at one time strongly urged this source, 
 and thought that he had found in the cows the strep- 
 tococcus or diplococcus which he believed was the 
 cause of the disease. But his observations have not 
 been verified, and it is generally believed at the pre- 
 sent time that milk receives scarlet fever infection 
 from human sources exclusively. 
 
 While it is certain that occasionally extensive and 
 spectacular outbreaks of scarlet fever are caused by 
 infected milk, and that every effort should be made to 
 prevent such milk infection, it is equally certain that 
 milk infection plays but an infinitesimal part in the 
 epidemiology of scarlet fever. 
 
 SUMMARY. 
 
 1. The micro-organism which presumably is the 
 cause of scarlet fever is unknown. 
 
 2. Evidence points to scarlet fever as a local dis- 
 ease of the throat and nose, as is diphtheria. 
 
 3. The rash and desquamation are more likely to 
 be due to the action of a toxin than to the presence of 
 the pathogenic organism in the skin. 
 
 4. The incubation, or more properly latent period, 
 of scarlet fever is usually short, but may be prolonged 
 
 for weeks. 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 49 
 
 5. Scarlet fever is infectious with the appearance 
 of the first symptoms. The height of the infectivity 
 is coincident with activity of the throat symptoms. It 
 then rapidly declines. In a small proportion of cases 
 it may persist for months. 
 
 6. Prolonged infectivity is often associated with 
 the persistence of the pathologic process in throat, 
 nose and ear. 
 
 7. The secretions of the throat and nose are 
 probably the chief source of infection. 
 
 8. The exfoliated epidermis is probably not infec- 
 tious. 
 
 9. The infectivity of the disease is less than is 
 generally believed. 
 
 10. In the great majority of cases scarlet fever ex- 
 tends by contact infection. 
 
 11. Infection by fomites is of little importance. 
 
 12. Except by droplet infection, which has a very 
 limited range, scarlet fever is probably almost never 
 an airborne disease. 
 
 13. Milk infection though a real danger, is the 
 source of comparatively few cases. 
 
50 THE MODE OF INFECTION AND DURATION OF 
 
 REFERENCES. 
 
 (1) Mallory, Jour. Med. Research, Jan., 1904. 
 
 (2) Gamaleia, Berl. klin. Woch. 1908, XLV, s. 1T95. 
 
 (3) Boston Med. and Surg. Jour. May 22, and 29, 1902, pp. 533 and 561. 
 
 (4) Murchison, Clin. Soc. Trans., 1878, XI, 238. 
 
 (5) Acute Contagious Diseases p. 264. 
 
 (o) Barlow, Practitioner, Lond., Dec, 1907. 
 
 (7) Zilgien Med. infantile, Par., 1908, V., p. 105. 
 
 (8) Turner, Report on Return Cases of Scarlet Fever and Diphtheria 
 in London, 1902-4, p. 3. 
 
 (9) Cameron, Rep. on Return Cases of Scarlet Fever and Diphtheria 
 in London, 1901-2, p. 4. 
 
 (10) Turner' s Report on Return Cases of Scarlet Fever and Diphtheria 
 in London, 1902-4, p. 18. 
 
 (11) ISTewsholme, Med. Chirurg. Trans., Vol. 87. 
 
 (12) Cameron Rep. on Return Cases of Scarlet Fever and Diphtheria 
 in London, 1901-2, p. 98. 
 
 (13) Simpson, Report on Return Cases of Scarlet Fever and Diph- 
 theria in London, 1898-9, p. 16. 
 
 (14) Cameron, Report on Return Cases of Scarlet Fever and Diph- 
 theria in London, 1902-4, p. 27. 
 
 (15) Jurgensen, Scarlet Fever, Nothnagel's Encyclopedia, p. 420. 
 
 (16) Stickler, N. Y., Med. Rec, 1899, II, p. 363. 
 
 (17) Grunbaum, Br. Med. Jour. 1904, I, p. 816. 
 
 (18) Cameron, Report on Return Cases Scarlet Fever and Diphtheria 
 Lend., 1901-2, p. 13. 
 
THE INFECTIOUS PERIOD IN SCARLET FEVER. 51 
 
 (19) Cameron, Report on Return Cases Scarlet fever and Diphtheria, 
 Lond., 1901-2, pp. 38 and 79. 
 
 (20 
 
 (21 
 Lond 
 
 (22 
 
 (23 
 
 (24 
 
 (25 
 
 (26 
 
 (27: 
 
 (28 
 Lond 
 
 (29 
 
 (30 
 
 (31 
 Lond 
 
 (32 
 
 (33 
 
 (34 
 
 (35 
 
 (36 
 1903. 
 
 (37 
 
 (88 
 
 Newaholme, Jour. Hyg., 1902, II, p. 150. 
 
 Cameron, Report on Return Cases Scarlet Fever and Diphtheria, 
 , 1901-2, p. 90. 
 
 Ibid., p. 18. 
 
 Boobbyer, Brit. Med. Jour., Aug. 31, 1895, p. 523. 
 
 Richards, Ibid, p. 524. 
 
 Gilbert, Brit. Med. Jour., Sept. 14, 1895. 
 
 Millard, Lancet, Apr. 5, 1902, p. 959. 
 
 Lauder, Lancet, Mar. 12, 1904, p. 712. 
 
 Cameron, Report on Return Cases Scarlet Fever and Diphtheria, 
 , 1901-2, p. 19. 
 
 Bond, Public Health, XV, p. 244. 
 
 Moore, Public Health, XXI, p. 148. 
 
 Turner, Report on Return Cases Scarlet Fever and Diphtheria, 
 , 1902-4, p. 6. 
 
 Lemoine, Bull, de la soc. med. milit. fran9ois0, 1907, p. 399. 
 
 Priestly, Trans. Epidem.Soc, 1894-5, XIV. 
 
 Lauder, Lancet 1904, i., p. 712. 
 
 Millard, Br. Med. Jour., Sept. 3, 1898. 
 
 Gaziot. Soc. med. des hop., July 3, 1903. Sem. med., June 24, 
 Caducee, Par. 1903, III, p. 273. 
 
 The Acute Infectious Diseases, p. 390. 
 
 Cameron, Report on Return Oases Scarlet Fever and Diphtheria 
 
 in London, 1901-2, p. 78. 
 
 (39) Report on the Health of the City of Manchester, 1906, p. 43. 
 
52 INFECTIOUS PEBIOD IN SCAKLBT FEVER. 
 
 (40) London, Kep. of Med. Of. of Health to Co. Council, 1904, p. 27, 
 
 (41) Cameron, Report on Return Cases Scarlet Fever and Diphtheria, 
 London. 1901-2, p. 128. 
 
 (42) Jour. Am. Med. Asso., 1906, XVII, p. 574. 
 
 (43) Rev. de hyg., Paris, 1907, XXIX, p. 1057 and Bull, et mem. see. 
 med. des. hop., 1909, XXVI, p. 588. 
 
 (44) Cameron, Report on Return Cases of Scarlet Fever and Diph- 
 theria, London, 1901-2, p. 37. 
 
 (46) The Acute Infectious Diseases, p. 346. 
 
 (46) Tarnissier La sem. med,, 1903, p. 267. 
 
 (47) Med. and Surg. Rep. of Boston City Hospital, 1897. 
 
 (48) Rev. d'hyg. 20 Mass. 1903, p. 256. Bull. med. 19 Mass., 1904, 
 p. 251. 
 
 (49) Hyg. Lab. Bull. No. 41, U. S. P. H. & M. H. S. 
 
 (50) Ibid, p. 94. 
 
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