METHODS OF EXAMINATION 351 



interesting fact may be mentioned, namely, that Eoger and 

 Garnier found evidence of the liver and spleen having special 

 capacities for killing anthrax bacilli ; an otherwise fatal dose 

 could be introduced into the portal vein or the splenic artery 

 without causing death. It has been thought that the capsule 

 of the anthrax bacillus is a defensive mechanism against 

 bactericidal capacities in an infected animal. It is stated that 

 capsulation renders the bacillus less susceptible to phagocytosis. 

 In certain anti-anthrax sera precipitins for the bacilli are stated 

 to be present, but the investigation of such sera by the com- 

 plement deviation method has not furnished convincing 

 evidence of the presence of anti-bodies. 



Methods of Examination. — (a) Microscopic Examination. — In a case of 

 suspected malignant pustule, film preparations should be made from the 

 fluid in the vesicles or from a scraping of the incised or excised pustule, 

 and stained by Gram's method. In this way practically conclusive 

 evidence may be obtained. McFadyean's methylene-blue method (p. 335) 

 should also be applied. Occasionally bacilli are so scanty that both film 

 preparations made from different parts and even cultures may give 

 negative results, and yet a few bacilli may be found when a section of the 

 puitule is examined. Care ought to be taken in manipulating a pustule 

 before excision, as, otherwise, the diffusion of the bacilli into the sur- 

 rounding tissues may be aided. The examination of the blood in cases 

 of anthrax in man usually gives negative results, with the exception of 

 very severe cases, when a few bacilli may be found in the blood shortly 

 before death. 



(b) Cultivation. — The material should be stroked on agar tubes. At 

 the end of twenty-four hours at 37° C. anthrax colonies will appear, and 

 from their wavy margins can be readily recognised by means of a hand 

 lens. 



While the isolation of the b. anthracis from fresh material is usually 

 easy, great difficulty may be encountered where the organism is to be 

 sought for, in, say, a carcase which has been dead for from twenty-four 

 to forty-eight hours, as the bacilli rapidly die out or are associated with 

 putrefactive organisms. In such cases methods have been applied with a 

 view to putting the organisms in specially favourable circumstances for 

 growth and especially for sporulation ; in one of these — the so-called 

 Strassburg method — the suspected blood or tissue juice is spread on moist 

 sterilised sticks of plaster of Paris and incubated in a moist chamber, and 

 Miiller and Engler have modified this by substituting for the plaster 

 sterilised pieces of flower-pot placed under similar conditions. 



(c) Test Inoculation. — A little of the suspected material mixed with 

 some sterile bouillon or water should be injected subcutaneously into a 

 guinea-pig or mouse. If anthrax bacilli are present, the animal usually 

 dies within two days, with the changes in internal organs already 

 described. The diagnosis of an organism as the anthrax bacillus cannot 

 be said to be substantiated till its pathogenicity has been proved. 



(d) Ascoli'x Thermo-preci/iitin Reaction. — This depends on the 

 observation that certain anthrax immune sera produce a precipitin 

 reaction with the products of the b. anthracis. The suspected blood or 

 tissue is boiled for a few minutes in five to ten volumes of normal saline 



