6oo Erste Sitzung der fünften und zehnten Sektion. 



We see then that in many special cases certain parts or tissues 

 grow independently of the rest of the organism and their growth 

 is regulated by or caused 03^ specific secretions or "hormones". 

 And we have also seen above that in the normal growth of cer- 

 tain animals the parts or tissues grow separately — there is no 

 such thing as the growth of the animal as a whole. It seems quite 

 likely therefore, that in organisms in general the normal 

 growth of each tissue or even each organ is 

 controlled separately by a specific internal 

 secretion. These substances may regulate growth either 

 through inhibition or acceleration and the effect produced may 

 be due either to the presence or the withdrawal of the specific 

 substance. 



In conclusion we might add that from the point of view of 

 this conception of normal growth the relation between determi- 

 nate and indeterminate growth becomes interesting and easily 

 explained. Among the indeterminately growing vertebrates the 

 brain, heart, and most of the other viscera diminish their rate 

 of growth at a more considerable rate than do the muscles and 

 connective tissues. Consequently, among the larger individuals 

 these latter tissues tend to outgrow the Controlling and nutri- 

 tive organs and a lack of physiological balance results. The slowly 

 growing brain, digestive glands, and fins become no longer ad- 

 equate to maintain the more rapidly growing connective tissues 

 and muscles and the organism soon comes to lack unity of phy- 

 siological Organization, death resulting either directly or indi- 

 rectly. The formation of a specific internal secretion tending to 

 inhibit the growth of the muscles and connective tissues, or the 

 withdrawal of a substance which stimulated their growth would 

 result in the condition of determinate growth. Then the growth 

 of these bulky tissues having been stopped within the limits of 

 the physiological efficiency of the nutritive and Controlling mecha- 

 nisms, the organism might remain alive for a long period after 

 growth has been practically completed, final senescence and death 

 then resulting from other causes. 



Diskussion: 



Herr Prof. Dr. A. B i e d 1 (Wien) verweist darauf, daß das 

 Wachstum sicherlich von mehreren Faktoren abhängig ist: Einer- 

 seits von den Bedingungen der günstigsten Assimilation (Ernäh- 

 rung, Temperatur, Muskelarbeit usw.) und andererseits von der 

 Tätigkeit der innersekretorischen Organe. Die Schilddrüse, Neben- 

 niere, Hypophyse, Keimdrüsen, Thymus und noch andere Organe 

 produzieren wachstumsanregende und wachstumshemmende Hor- 

 mone und beeinflussen somit auf chemisch-korrelativem W 7 ege das 

 Wachstum einzelner Organe und des ganzen Körpers. Es muß 



