246 PHARMACEUTICAL BACTKRIOLOGY 



lar reactions are observed with milk and egg albumen, when used with 

 their specific immune sera. These reactions have been utilized to secure 

 evidence in criminal cases. The serum of an animal which has been in- 

 jected with human blood (humanized immune serum) produces a precipitate 

 when mixed with human blood, even in high dilutions. Like agglutina- 

 tion, the reaction is, however, not wholly specific. For example, human- 

 ized animal serum will also produce a precipitate with the blood of higher 

 apes. Dog immunized animal serum will produce a precipitate with wolf's 

 blood, etc. 



The chief immunizing agents are the bacterolysins, the antitoxins and 

 the leucocytes (phagocytes) aidedi by the opsonins. The significance of 

 agglutinins and precipitins in the prevention of bacterial disease is not 

 clear. 



Recent observations on drug action tend to prove that some of these 

 remedial agents apparently possess antitoxic and other immunizing prop- 

 erties. It is for example fairly well proven that phosphorus and Echi- 

 nacea angustifolia have the power of increasing the opsonic index in 

 certain bacterial invasions. Sulphide of carbon and silica appear to check 

 and cure suppurative processes, perhaps due to similar activity. Nuclein 

 which is usually derived from yeast, is reported to be decidedly bactericidal 

 and to increase phagocytosis to a marked degree. According to Lloyd, 

 Lobelia, when administered hypodermically, counteracts the toxin of the 

 diphtheria bacillus, being similar in its efl'ects to the antidiphtheric serum 

 (antitoxin of diphtheria;. Belladonna is reported to be prophylactic 

 as well as curative in scarlet fever. It is highly probable that as our knowl- , 

 edge of the therapeutic action of drugs develops, there will be a complete 

 revolution in their use as remedial agents. 



2. The Immunizing AgeHts. — The following is a brief description of 

 the more important immunizing agents of the body. Other immunizing 

 agents will be given in Chapters XI and XII. 



a. Phagocytosis. — ^As already explained Metschnikoff made the interest- 

 ing discovery that the white blood corpuscles (leucocytes) seized upon and 

 disintegrated and fed upon bacteria with which they came in contact or 

 with which they were brought in contact. Not only do the leucocytes 

 possess this power but also other body cells, as the endothelial cells of 

 capillaries, and the ; lymphocytes which are cellular structures of the 

 lymph channels corresponding to and developing into leucocytes upon 

 entering the circulation, certain fixed body cells, more especially the epithe- 

 lial cells of the intestinal tract and of mouth and throat or upper respira- 

 tory tract. 



The germ devouring property of leucocytes (phagocytosis or leucocy- 

 tosis of Metschnikoff) is typically illustrated in an injury to the skin, 



