IMMUNOLOGY. IMMUNITY AND IMMUNIZING AGENTS 



257 



in cancer, in goiter, in chronic eczema, in tuberculosis, in hay fever and in 

 other intractable diseases. 



An animal (as rabbit or guinea pig) which has been sensitized to any 

 specific substance, as human blood, deer's blood, egg albumm, casein, 

 cow's milk, goat's milk, horse serum, specific plant extracts, poisons 

 of many kinds, etc., wiU show a skin reaction toward the specific substance 

 for which it was sensitized. One and the same animal may in fact be 

 sensitized to three or more substances at the same time and will show a 

 separate and distinct and specific reaction for each substance. The 

 specificity fails or rather merges or blends with many closely related 

 substances. Thus a guinea pig sensitized to human blood will react 

 toward the blood of the ape. Other interacting sensitizations develop 

 toward rat and mouse, dog and wolf, horse and ass, sheep and goat. 

 Organ specificity is also highly interesting and gives some apparently 

 contradictory results. For instance, a guinea pig sensitized to cerebral 

 extract of a rabbit will react toward the cerebral extract of widely dif- 

 ferent species, but will not react toward other tissues. 



It may indeed be possible to sensitize one animal toward a large 

 number of substances and such animal may then be employed for making 

 skin reaction tests with any one or all of the substances in question. 

 Thus the physician could use this animal for diagnostic purposes; the 

 criminologist to ascertain whether or not a given blood stain was of 

 human origin; the food analyst to determine whether or not the albumen 

 is from duck's eggs or from hen's eggs; the pathologist for the purpose 

 of ascertaining the malignancy or benignancy of a tumor; the bacteri- 

 ologist to determine the group relationship of a given microorganism; the 

 toxicologist to ascertain the identity of a poison, etc. 



Bacteriolysins. 

 Inherited or normal 



Natural 



Immunizing 

 Agents 



Active 



Opsonins. 

 Phagocytes. 

 Glandular secretions 



Augmented — Immunizing diseases. 



Artificial 



Modified toxins and un- 

 modified toxins. 



Toxins. 



Small-pox vaccina- 

 tion. 

 , Rabies vaccination. 



Bacterial — Bacterins or vaccines. 



Passive 



Sera — Diphtheric, tetanic, glandular extracts, etc. 

 Drugs— Nuclein, lobelia, phosphorus, etc. 



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