THE LIMITS OF SERUM-THERAPY. 757 



cautions. Brodie has found, however, that, of all sera obtained 

 from domestic animals, horse-serum was the least toxic. On 

 the whole, the literature of *thie therapeutic method and the 

 foregoing line of reasoning seem to us to warrant the following 

 conclusions: 



The normal serum of certain animals, particularly the horse, 

 ox, cow, goat, and dog, contains enough fibrinogen to render its use 

 in small and frequently repeated doses advantageous in febrile 

 processes attended with hypoleucocytosis and an excess of trypsin. 

 Horse-serum, being the least toxic, should be given the preference. 



Diphtheria, the only disease which may be said to have 

 found in antitoxin, thanks mainly to the splendid labors of 

 Behring, a specific antagonist, presents, it seems to us, patho- 

 logical characteristics of an opposite order. Here leucocytosis 

 is a prominent feature of the morbid process, as long as the 

 adrenal system is functionally overactive, and, since antitoxin 

 does prove unquestionably effective when the whole subject is 

 studied with due care, it follows, if our views are sound, that 

 the neutrophiles are able to furnish the blood with enough 

 fibrinogen to afford, in conjunction with the oxidizing sub- 

 stance, the heat-energy required by the trypsin which the in- 

 jected antitoxin contains. Such being the case, the disease 

 must follow a lethal course merely because of the lack of tryp- 

 sin. How is this absence of trypsin engendered, or, if there 

 is trypsin in the child's plasma, why does it fail to antagonize 

 the pathogenic elements? 



A feature emphasized by Metchnikoff, and that our anal- 

 ysis has sustained, is the absence of trypsin from the plasma. 

 According to our own interpretation of experimentally demon- 

 strated facts, such a condition of the blood only occurs when 

 it is completely devoid of morbific products of digestion wastes 

 which the leucocytes themselves cannot submit to complete 

 cleavage. Briefly, it may be said that under normal conditions 

 the blood does not contain trypsin. And this may be demon- 

 strated by a very familiar bacteriological fact: i.e., that, using 

 Stengel's words, "the most characteristic cultures are obtained 

 upon blood-serum." 



A direct application of this fact, however, would mislead 

 us. In other words, we cannot say that it is because the blood 



