May 28, 1897.] 



SCIENCE. 



825 



for securing increased resistance to disease 

 or better pathological adaptations. 



It would be interesting to continue our 

 ■consideration of the compensatory hj^er- 

 trophies by an examination of those of 

 glandular organs from points of view simi- 

 lar to those adopted for the heart. For 

 the kidney, at least, the materials are at 

 hand for such a purpose, but, as I desire in 

 the limited time at my disposal to touch 

 upon other varieties of pathological adapta- 

 tion, I must refer those interested especially 

 to the investigations of Grawitz and Israel, 

 Ribbert, N'othnagel and Sacerdotti as to the 

 conditions underlying compensatory hyper- 

 trophy of the kidney. I can likewise 

 merely call attention to the interesting re- 

 searches of Ponfick upon the most wonder- 

 ful of the compensatory hypertrophies in 

 higher animals, that of the liver. Ponfick, 

 as is well known, has demonstrated that, 

 after removal of three-fourths of this organ, 

 new liver-substance, with normal functions, 

 is recreated from the remainder and to an 

 amount nearly equalling that which was lost. 



The chapter of pathological adaptations 

 in bones and joints I shall leave untouched, 

 notwithstanding the admirable illustrations 

 which might be drawn from this domain. 



There is no more fascinating field for the 

 study of pathological adaptations with re- 

 ference to the mechanical factors involved 

 than that furnished by the blood-vessels, as 

 has been shown especially by the brilliant 

 researches of Thoma. "With wonderful 

 precision can a vessel or system of vessels 

 adjust itself to changes in the pressure, 

 velocity and quantity of blood, and thereby 

 serve the needs of the tissues for blood. 

 Under pathological, as well as phj'siological, 

 conditions this adjustment may be brought 

 about not only through the agency of vaso- 

 motor nerves and the physical properties of 

 the vascular wall, but also, when the neces- 

 sity arises, by changes in the structure of 

 the wall. 



The changes in the circulation introduced 

 by the falling-out of the placental system at 

 birth are essentially the same as those re- 

 sulting from amputation of an extremity, 

 and the consequent alterations in the struc- 

 ture of the umbilical artery are identical 

 with those in the main artery of the stump 

 after amputation. The closure of the 

 ductus Botalli and the ductus venosus soon 

 after birth, and, still better, transforma- 

 tions of vessels in the embryo, furnish 

 physiological paradigms for the develop- 

 ment of a collateral circulation. Many 

 other illustrations might be cited, did time 

 permit, to show that in the processes of 

 normal development, growth and regressive 

 metamorphosis of parts, both before and 

 after birth, and in menstruation and preg- 

 nancy, changed conditions of the circulation, 

 arise analogous to certain ones observed 

 under pathological circumstances, and that 

 the mode of adjustment to these changes by 

 means of anatomical alterations in the 

 vessels may be essentially the same in the 

 physiological as in the morbid state. I see 

 in these facts an explanation of the relative 

 perfection of certain vascular adaptations 

 to pathological or artificial states, as may 

 be exemplified by changes in a ligated 

 artery and by the development of a col- 

 lateral circulation.- The mechanisms by 

 which the adjustments are secured have, in 

 consequence of their physiological uses, for 

 reasons already explained, a special fitness 

 to meet certain pathological conditions. 

 That this fitness should be greater in youth 

 than in old age is in accordance with laws 

 of life, indicated with especial clearness by 

 Minot in his interesting studies on ' Senes- 

 cence and Rejuvenation.' 



But these mechanisms are not equally 

 well adapted to meet all morbid changes in 

 the vessels. Although Thoma's interpreta- 

 tion of the fibrous thickening of the inner 

 lining of vessels in arterio-sclerosis and 

 aneurism, as compensatory, or, as I should 



