SCHULTZ AND JORDAN: STUDIES IN ANAPHYLAXIS 75 



animal may or may not recover, depending upon the gravity of 

 the symptoms elicited by the toxic dose of serum. For example 

 there was observed in one sensitized opossum, under ether anes- 

 thesia, a sharp fall of blood pressure from 122 to that of 20 mm. 

 of mercury, at which latter level the pressure remained for three 

 or more minutes. The respiration changed from a rate of 44 per 

 minute, before the fall of blood pressure, to one of 54 during the 

 fall, with a diminished respiratory output. As soon as the blood 

 pressure reached its lowest level the respiration was greatly slowed 

 and increased in force. The oscillation of the intrapleural pres- 

 sure was also greatly increased and accompanied by a gradually 

 increased inspriatory period until finally respiration ceased in the 

 semi-inspiratory stage; whereupon the animal, after some min- 

 utes, gave a series of gasps and recovered, whereas in another 

 animal the respiratory gasps were absent and the animal failed 

 to recover. 



The blood vessels of the opossum's lung react much as do those 

 of the guinea-pig while the bronchi react more like those of the 

 cat-lung. 



One of the most interesting phenomena observed in one highly 

 sensitized animal, but which may not prove to be characteristic 

 of the anaphylactic opossum, is the reaction of the blood. In this 

 animal the arterial blood became milk-red in appearance and upon 

 bleeding the animal a milk-like layer floated to the surface and 

 was pipetted off. If the horse serum was present in large quan- 

 tities in a large blood vessel masses of the white material seemed 

 present and in time became tough, but where the serum was more 

 thoroughly mixed with large quantities of blood the particles as 

 seen thru the microscope were extremely small. This very finely 

 divided emulsion when dried as a film upon a cover slip revealed 

 a rich supply of fat droplets after staining with Sudan III, or 

 with osmic acid. There was also other material, the nature of 

 which has not yet been determined, but which took Hasting's 

 and also Wright's stain and appeared like cellular and protein 

 debris. Animals that did not prove to be hypersensitive toward 

 horse serum yielded a fat layer in the blood, to about the same 

 extent as does cat-blood, but so far the phenomenon to which 



