PROTECTIVE FERMENTS 107 



against placental tissue. This observation, which has now been con- 

 firmed in several thousand cases and which has given rise to a most 

 important diagnostic method (see Abderhalden's pregnancy test), 

 has furnished the basis for an immense amount of experimental 

 work which is now in progress and which bids fair to yield results of 

 the greatest interest to medicine. To judge from what has already 

 been accomplished it would appear that proteolytic ferments endowed 

 with a high degree of specificity appear in the blood not only when 

 actual cell destruction is going on, i. e., not only in organic disease 

 of the body, but, under certain conditions even, when the functional 

 activity of an organ is at fault (see Ferment Reactions under Patho- 

 logical Conditions) . Regarding the nature of the ferments in question 

 and the place of their formation our knowledge is as yet but meager. 

 While some writers maintain that they have amboceptor character 

 and can be reactivated after destruction of the native complement 

 by the addition of fresh complement, Abderhalden denies this and 

 regards them as antibodies sui generis. That they may be formed 

 by the organs against which their activity is directed would appear 

 from the interesting observation of Abderhalden that the intraperi- 

 toneal injection of inactivated testicular tissue does not call forth the 

 appearance of antitesticular ferment in castrated animals, while it 

 does so quite readily in the normal. 



The brief survey of the manner in which the animal body responds 

 to the parenteral introduction of foreign cells and cell derivatives, 

 which has just been given, imperfect and condensed though it be, is 

 probably sufficient to show that a field of work has been opened up 

 which offers a most alluring perspective to the investigator, both in 

 medicine and general biology. During the few years that it has 

 been tilled, the returns have already been wonderful in their diver- 

 sity and value, and we have every reason to suppose that a great deal 

 of the future progress of medicine will lie in this direction. We have 

 already a host of experimental facts which only await their proper 

 interpretation, before they will become important stepping stones 

 toward still more important findings. Among the many able investi- 

 gators who are closely associated with progress along these Hues, one 

 stands out prominently above all others, because he has furnished 

 us with a working hypothesis which satisfactorily explains many 

 observations that have been made in this field, and because its study 



