*32 R. G. HOSKINS 



suprarenal glands nor by stimulation of their secretory nerve can more than 

 a very moderate rise of blood pressure be evoked. In view of the fact 

 that the qualitative reaction to epinephrin may be exactly reversed by 

 changes in the quantity administered, this factor is of considerable theo- 

 retical importance. 



Another difficulty is that abnormal products undoubtedly vary greatly 

 from one extract to another, even of the same gland. Among the factors 

 which may cause such variation are the time that elapsed between the 

 preparation and use of the extract, the degree of autolysis or even putre- 

 faction, the dilution, the degree of heat used in preliminary processes, 

 and preservatives added. In the presence of so many variables and these 

 often quite uncontrolled, how can any valid conclusions be drawn? It is 

 obvious that the utmost caution must be observed. At most such experi- 

 ments serve merely to demonstrate pharmacodynamic constituents in the 

 extracts as finally prepared. This is merely a first step in the demon- 

 stration of the existence of a hormone. Positive results establish no more 

 than a certain degree of antecedent probability that a hormone is present. 

 It remains to be proved that the active substance is not an artefact or that 

 it exists in the blood or lymph coming from the organ in question. 



Despite the inherent defects in the method of intravenous injections 

 and the frequently enunciated warnings against the numerous sources of 

 error in the use of the method, the literature discloses a voluminous series 

 of reports of researches based on such injections. Nor have the authors 

 hesitated in many cases to offer sweeping deductions from observations 

 so obtained. As recently as 1JHS iMarfori published an elaborate paper 

 in a leading biological journal, announcing the discovery of a new hor- 

 mone, u lymphogangline," elaborated by the lymphatic glands. The ob- 

 servations upon which the claim is founded are essentially that extracts 

 of lymphatic glands reduce the frequency of the heart beats, lower the 

 Mood pressure, contract the pupil, and hinder the production of epinephrin 

 irlycosuria. This paper is reviewed at length by Vincent (1918). If 

 one were to grant the validity of such claims, the number of hormones 

 in the- hndv is limited only by the patience and skill of the investigator in 

 isolating tissue components. There is little doubt that similar "hormones" 

 <-"ii!d l.e isolated from the vocal cords, from the vermiform appendix, 

 from the iris, or any other body tissue. 



While it is historically true that many significant data have been 



ained l,v the method of intravenous injections of tissue extracts, yet it 



* obvious fro,,, the foregoing discussion that from such experiments alone 



' tentative conclusions can he drawn and that the investigator must be 

 rigidly on his -uard against pitfalls at every step. 



Ut in spite of the inherent sources of error in the use of gland 



v vein, many instructive results may be obtained from this type 



.'xperimentation. It has certain outstanding advantages. Any hormone 



