METHODS OF EXAMINATION 317 



facts have long been known; for example, in the dog, which 

 shows great natural resistance, the serum has little if any 

 bactericidal action, while in the susceptible rabbit there is 

 present a serum capable of killing the organism. Such observa- 

 tions have hitherto been without explanation. Again the 

 properties of the serum of immune animals have been much 

 discussed. Sobernheim and others have been unable to detect 

 in it any trace of special bactericidal action. Sclavo found that 

 the serum when heated to 55 C. did not lose its protective 

 properties ; as the serum might have been complemented (see 

 Immunity) by the serum of the animal into which it was injected, 

 he simultaneously introduced an anti-complementary serum and 

 found that the heated serum was still effectual. From this he 

 deduces that in the action of the serum substances of the nature 

 of immune body and complement are not concerned. Many 

 have thought that the serum had a stimulating effect on the 

 leucocytes, but Cler has brought forward ground for supposing 

 that its effect is a sensitising one on the bacteria, and that thus 

 the effects are to be traced to opsonic action. With regard to 

 the formation of the protective substances, it is stated that the 

 spleen and bone-marrow are richer in these than the blood fluids. 

 In this connection an interesting fact may be mentioned, namely, 

 that Roger and Gamier 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. 



Methods of Examination. These include (a) microscopic 

 examination ; (b) the making of cultures ; and (c) test in- 

 oculations. 



(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 with a watery solution of methylene-blue 

 and also by Gram's method. By this method practically con- 

 clusive evidence may be obtained ; but sometimes the result is 

 doubtful, as the bacilli may be very few in number. In all 

 cases confirmatory evidence should be obtained by culture. 

 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 pustule is examined. It should be noted that the greatest 

 care ought to be taken in manipulating a pustule before excision, 

 as the diffusion of. the bacilli into the surrounding tissues may 

 be aided and the condition greatly aggravated. The examination 



