256 Hypertrophy. 



one kidney is removed in an experiment, in the course of but a few 

 days thereafter the other begins to enlarge ; and it is not infrequent 

 in slaughtered animals to find one kidney shrunken up and the other 

 from one to two-thirds larger than the normal organ. The reason 

 that the increase in volume does not reach double the normal is 

 because all of the constituent elements do not hypertrophy in even 

 proportion, the process involving particularly tlie secretory struc- 

 tures, the glomeruli and the convoluted tubules, the epithelial cells 

 of w^hich enlarge and the coils become more intricately convoluted 

 and therefore longer. Of course compensation for a functional dis- 

 turbance of a gland by hypertrophy can result only in case there 

 exist analogous tissue or a glandular rest."-^' In this sense the 

 lymph glands and the bone marrow, for example, might substitute 

 for loss of the spleen, but not other kinds of glands. 



As a reason why glandular organs are forced to higher secretory 

 activity in case of removal of a portion of their parenchyma, it may 

 be assumed that following the ablation of the organic parenchyma 

 there accumulate in the blood certain secretory stimulants, sub- 

 stances which stimulate the gland cells. \\'hether these substances 

 act directly on tlie protoplasm to stimulate it to productive activity, 

 or whether the more active protoplasm takes up more nutritive ma- 

 terial and is therefore enabled to throw off more products, is un- 

 certain (Ribbert). The fact that muscles in a state of increased 

 activity receive an augmented blood supply and in case of destruc- 

 tive changes in an organ a similar hypersemia develops in its remain- 

 ing tissue (due to the accumulation of materials no longer se- 

 creted) suggests according to Ribbert an explanation for the oc- 

 currence of hypertrophy, in that the persistent congestion distends 

 the tissue, with the result of separating the individual cells from 

 each other and thus gives origin to space for the increase of vol- 

 ume and for the multiplication of cells. Not only is it to be sup- 

 posed that free spaces exist between the cells but the protoplasm 

 itself is substantially distended, its individual molecules separated 

 from each other and this intracellular increase of space affords op- 

 portunity for assumption of further elements which go to make 

 up the protoplasm. Ribbert's theory of mechanical origin of tissue 

 growth (cf. Regeneration) finds special applicability in the devel- 

 opment of cardiac hypertrophy and the hypertrophy of muscular 



♦ [What is meant here is the persistence in undeveloped form of tissue 

 capable of taking up the morpholoR>' and function ot the adult tissue which 

 has been lost. TTnus in the formation of an organ there may be embryonic 

 elements in excess which are not employed in the formation or subsequent 

 development of the organ, remaining- as "rests" and undifferentiated. In 

 case of loss of substance of the organ such representatives may perhaps develop 

 to maturity and compensate for the destroyed portions.] 



