MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 849 



after the manner of a true diffusible or soluble toxin. Agar streak cultures show an 

 abundant filiform whitish or bluish-gray translucent growth with no special char- 

 acteristics. Broth is uniformly and moderately clouded and only occasionally a 

 delicate pellicle may develop. Gelatin colonies are bluish white in color, trans- 

 parent and with somewhat notched margins. Stab cultures show more growth at 

 the surface, while in the depth the growth is filiform and less abundant. The 

 medium is not liquefied. Milk is not coagulated. In litmus milk there may be a 

 trace of acid formed at first, followed by a return to neutral or very slightly alkaline 

 reaction. Potato was at one time considered a very valuable differential medium. 

 The growth of the bacillus upon it is quite abundant, glistening, but invisible, 

 when the potato is acid. A more alkaline reaction allows a rather heavy yellowish 

 growth indistinguishable from B. coli. Special media are used in the cultivation 

 of the typhoid bacillus, chiefly for differential purposes. The cultural features on 

 these do not show sufficiently striking characters to make it worth while to review 

 the many that have been devised. Specific agglutinating and bacteriolytic sera 

 as well as the complement binding reaction are valuable aids in identifying the 

 bacillus. Resistance to heat and light is not different from that of the average non- 

 spore-bearing species. Its thermal death-point is about 56 for ten minutes, 60 

 for one minute. Exceptionally resistant forms have been found alive in ice after 

 three months. Sometimes the bacilli will remain viable for a month after drying. 

 At other times they die out rapidly. They have been found to be viable for ten 

 days in distilled water, while pure sodium chloride dissolved exerted an unfavorable 

 influence. In faeces the length of life is from a few hours to several days, or even as 

 high as five months in winter. Their life in privies and cesspools is ordinarily 

 brief but has been found to extend for thirty days. Of the non-spore-formers 

 the bacillus appears to be rather more resistant than the average but succumbs 

 within five minutes to i : 5000 mercuric chloride or 5 per cent phenol. 



The organism enters the body through the mouth by means of 

 infected fingers, food, milk, and water, etc. 



On reaching the intestine the organism probably propagates to some 

 extent before penetrating the intestinal mucosa. It enters into the 

 blood stream and is disseminated throughout the body. According 

 to the endotoxin theory it must slowly be dissolved by the lytic sub- 

 stances which have been gradually accumulating in response to the 

 primary intoxication.- 



The organisms have been cultivated from the rose spots and have 

 been found in vomit without the presence of blood, and in sputum. 

 Typhoid meningitis and osteitis occur occasionally. At autopsy the 

 'spleen and gall-bladder yield the highest number of positive cultures. 

 It is of interest to note too that while the highest percentage (89-90 

 per cent) of positive blood cultures occurs in the first week and the 



