216 PHYSIOLOGY. 



The agglutinating serum acts most energetically at 55 or 60 C. 

 The active substance in the serum is precipitated by alcohol, it is 

 not destroyed by drying at a low temperature, and it dissolves in 

 water and glycerin. These are the properties also of enzymes. The 

 active substance here is agglutinin. Widal Reaction. The typhoid 

 patient's serum gives an agglutinating serum for homogeneous cul- 

 tures of the typhoid bacillus. 



PRECIPITINS TSCHISTOVITCH-UHLENHUTH TEST. 



When you inject under the skin or into the peritoneum of an 

 animal a, of species A, some cubic centimeters of blood-serum of 

 species B, and repeat the injection four or five times in the space 

 of five or six days, we find that blood-serum of the animal a has the 

 property, when mixed with the serum of the animal of species J5, to 

 cause a fine precipitate at the bottom of the mixture. If in place 

 of the injection of blood-serum, under the same conditions we inject 

 the albuminoid substances of the serum separated by precipitation 

 by ammonium sulphate and dissolved in saline 1 to 100, we find that 

 the serum of a has acquired the property of precipitating the serum 

 of the animal of the species B as before. This fact is used to 

 determine human blood by injecting the serum of human blood into 

 rabbits or dogs. We thus obtain precipitants for human blood, a 

 medico-legal test. This precipitate is destroyed by heat over 100 

 C.; it is not destroyed by drying at a low temperature; it is soluble 

 in water; it is precipitated by alcohol and by the salts precipitating 

 globulins. Tiiese are the properties of enzymes. It may be a zymoid. 



CYTOTOXINS. 



As to cytotoxins, we have seen in transfusion that blood foreign 

 to an animal dissolves its corpuscles (or cells); hence are called 

 haemolysins. The leucotoxins dissolve white blood-corpuscles. The 

 haemolysins act by separating the haemoglobin from the stroma of 

 the blood-corpuscles, making blood "laky." In fundamental charac- 

 ters the haemolysins, both natural and artificial, correspond to the 

 bacteriolysins. 



If you introduce into the peritoneal cavity of a guinea-pig, 

 which is strongly immunized against a vibrio of cholera, an emulsion 

 of this vibrio obtained by putting into a saline solution, 1 to 100, 

 a 24-hour culture of the cholera vibrio upon. gelatin, it will be found, 

 on withdrawing a little of the peritoneal fluid, after half an hour, 

 that the vibrios injected have lost their motion, are transformed into 



