PRACTICAL APPLICATIONS 407 



suitable objects for the study of phagocytosis. They are taken up 

 with great rapidity, and quickly undergo solution within the 

 leucocyte, first losing their sharp outline and power of retaining 

 Gram's stain, and disappearing altogether in ten minutes or less. 

 This makes the study of the opsonic index a matter of some 

 difficulty, which can be overcome by using isolated spores in test- 

 tube experiments. When no serum is used very few bacilli or 

 spores are taken up, and before the discovery of the opsonins 

 Metchnikoff noted that when rats are injected on the one side 

 with anthrax bacilli and on the other with the same organisms 

 mixed with blood-serum, oedema occurs only at the former place, 

 and it is from this that generalization occurs. Sawtchenko also 

 found that when the injection of the needle causes haemorrhage 

 the rat survives. The very careful and full researches of Metch- 

 nikoff on the degree of phagocytosis in susceptible and non- 

 susceptible animals are probably sufficient to lead us to believe 

 that the ingestion of the bacilli by the leucocytes is the all-im- 

 portant process in the cure of the disease, and the discovery of 

 the opsonins supplies the missing link necessary for us to account 

 for all the facts in a fairly satisfactory manner. We can only 

 conclude that the bactericidal effect of the serum plays a part of 

 comparatively small importance in combating the disease the 

 elaborate researches of Bail, Petterson, Sobernheim, etc., to the 

 contrary possibly, but by no means certainly, owing to the 

 absence of complement. 



The facts of passive immunity are not so fully explained. 

 There are, however, some reasons for thinking that the active 

 substance is an opsonin, perhaps a thermostable one. Thus 

 Sclavo's serum (according to Cler) will render bacilli fit for 

 ingestion after five hours' contact, and it does not lose its efficiency 

 on keeping. On the other hand, the remarkably rapid improve- 

 ment sometimes seen after the rise of Bandi's serum rather 

 suggests the presence of an antitoxin. 



Diagnosis. This is made in all cases by the demonstration of 

 the bacillus. 



Treatment. The preventive treatment is used for animals only. 

 Pasteur's method has already been noticed : it has been largely 

 used, and the results have, on the whole, been good. The 

 mortality from the inoculation is about \ per cent, of all cases, 

 but in some herds the number of deaths is much higher, and 

 serious loss is caused. The immunity is supposed to last for less 



