THE SUPRARENAL SYSTEM 245 



Serious changes in the aorta of rabbits after compression of 

 the abdominal aorta are described by W. Henwood Henry; and 

 Klotz observed similar changes in rabbits after they had been 

 repeatedly suspended with the head downwards. 



These experiments illustrate the important part played by 

 changed haemodynamic conditions in the etiology of lesions of 

 the vessel walls. They serve, moreover, to establish the prob- 

 ability of this agent as a factor in the causation of adrenalin 

 sclerosis. The discovery that similar changes are produced in the 

 vessel walls by other substances, whose property it is to increase 

 blood-pressure, such as digalen, digitoxin, strophantin, barium 

 chloride, ergotin, nicotine, and formaldehyde, may be regarded 

 as confirmatory evidence, although it is not possible in these 

 instances to exclude the operation of chemico-toxic factors. 



In spite of much searching investigation, it has not been 

 possible, up to the present, to arrive at any conclusive decision 

 concerning the pathogenesis of adrenalin arteriosclerosis. But 

 the increase and the fluctuation in pressure, on the one hand, and 

 the toxic injury to the vessel walls, on the other, are undoubted 

 factors in the causation of the condition. 



These findings are confirmed by the results of certain experi- 

 ments which I recently undertook, with the object of discovering 

 the changes brought about in the vessel walls by means of 1- and 

 d-suprarenin. I found that, when given in quantities too small to 

 provoke a rise in blood-pressure, serious sclerotic changes 

 followed the employment, not only of the 1-component whose 

 property it is to raise blood-pressure, but also of the d-component 

 which, owing to its slight toxicity, may be given in larger doses. 

 In no case did I find that treatment by subcutaneous injection of 

 d-suprarenin created a tolerance of subsequent intravenous injec- 

 tion of 1-suprarenin. The changes in the vessels to which 

 d-suprarenin gives rise are undoubtedly in the nature of toxic 

 injury, brought about by the agency of a substance, the affinity of 

 which to certain components of the vessel walls is suggested' by 

 certain experiments of A. Frohlich's, which have already been 

 described. 



The following facts are known concerning the part played 

 by certain physical conditions in the causation of a sclerosed 

 condition of the vessel walls. 



Pregnant animals appear to be less susceptible than others 

 to the influence of adrenalin (Loeb and Githens, Loeper, Boveri, 

 v. Koranyi). It is certain that the conditions of pregnancy, 

 castration (Thevenot), cachexia (L. Loeb and Githens, Pic and 

 Bonnamour), and fatigue (Thevenot), are not favourable to the 

 development of adrenalin lesions. During the period of lacta- 

 tion, the resistance to the action of adrenalin is lowered (Pic and 

 Bonnamour, Thevenot). As far as the effect upon thyroid- 

 ectomized animals is concerned, opinions are divided. It must 



