THE INFECTIOUS DISEASES. 23? 



water, which have been polluted with the excretions faeces and urin<^ 

 of persons suffering from the disease. Many serious epidemics of typhoid 

 fever have been traced to pollutions^ milk and drinking-water from 

 such sources. 1 



O ystptrs^ wh i ch have been taken from grossly polluted wntpr^ as near 

 sewen oppningp. have been the means of conveying the germs. " There 

 is abundant evidence that flies convey the infectious material from undis-^ 

 i 1 1 feet ed < lisHmrpvs,;' -^ 



lu milk the typhoid bacillus not only remains alive for long periods, 

 but undergoes n^fivAjnultiplication. It may remain long alive hi Avater, 

 and even for a time multiply. In the soil ^and when dried it may remain 

 alive for months. Frozen in icejt has been found alive after more than 

 three ^months. It is readily killed bv exposure-to strong sunlight. 



Preventive Inoculations. 



Preventive iiioculatiotis have been practised on a large scale in man by the method 

 of Haffkiue with apparently favorable results. In this method cultures of the bacillus 

 are killed by heat and the emulsion is injected subcutaueously. 



Agglutination. 



We have seen in an earlier section of this book (p. 190) that in the adaptation of a 

 living body to certain alien organic substances, among which are bacteria and their 

 toxins, the serum of the adapted or in the case of micro-organisms, of the immunized 

 individual may contain substances which are agglutinative for the particular species 

 of micro-organism involved. By the use of this phenomenon of agglutination, a method 

 of clinical diagnosis of considerable value has been devised and much employed espe- 

 cially in typhoid fever. 



The nature of this agglutination, which may occur with dead bacilli also, is cot 

 yet understood, nor is the reaction altogether limited to the bacterial species which in- 

 duces the tolerance. Furthermore, it appears that agglutination may be induced by 

 various organic and inorganic chemical substances. 



Agglutination has been used as a means of diagnosis in other infectious diseases. 

 It has been found useful also in the identification of species in various forms of bacteria. 4 



The Typhoid and Colon Bacillus. 



Much difficulty has been encountered in distinguishing between the typhoid ba- 

 cillus ana various lorms of the colon bacillusTwhjen they occur together, as may be the 



ease in (outain7hated__\vater or ni_tlHvjleje<-t<ijjf persons suiYering t'rom_tvj)hoid fever.. 

 As a result of this difficulty a very close relationship lias been assumed Jbetween tvjhojd 



1 Freeman, New York Medical Record, March 28th, 1896, bibliography; also 

 Vaugkc.n, Jour. Amer. Med. Assn., April 19th, 1902, p. 979. 



'Freeman, Albany Med. Annals, vol. xviii., 1897, bibliography; Mostly, Revue 

 d'Hygi&ne, t. xxii., pp. 12, 102, 193, 1900; Herdman and Boy ce, Thompson Yates Labo- 

 ratory Report, vol. ii. . supplement, 1899. 



3 See reference, p. 163; also report on typhoid fever in U. S. Military Camps during 

 Spanish War of 189S, by Reed, Vaughun, and Shakespeare, 1900; also experimental 

 study by Ficker, Arch. f. Hygiene, Bd. xlvi., 1903, p. 274. 



4 For further details of agglutination we refer to the special bibliography on the 

 subject, which may be found in Mace's "Bacteriologie." 1901, and to works on clinical 

 pathology, and for a comprehensive bibliography to Kohler, Klinisches Jahrbuch, Bd. 

 viii., 1901, p. 35. 



