RELATIONS OF THE ORGANS TO ONE ANOTHER. 611 



absolute proof of the destruction of blood-corpuscles, for it collects cellular 

 decomposition products from other organs. 1 Many observations make it 

 seem probable that the spleen is related in some way to bone-marrow. 

 These two substances can mutually aid one another. 



In discussing the individual organs we have lost sight of the chief con- 

 stituents of the entire organism, namely the muscles, nerves, and the con- 

 nective-tissue group. Of the latter, especially bone, cartilage, and true 

 connective-tissue, we scarcely assume any intimate relations with the other 

 organs, although undoubtedly such relations do exist. We are accustomed to 

 consider them merely as mechanically-acting structures, and for this reason 

 but little attempt has been made to ascertain what metabolic changes take 

 place within this group of tissues. As a rule, investigators have been con- 

 tent with the study of their chemical composition without attempting to 

 determine positively the extent to which they take part in the general metab- 

 olism. Now this connective-tissue group of substances takes part quite 

 extensively in building up the organism, and its functions are not always 

 the same. This is particularly true of connective-tissue itself, which, 

 according to its histological construction, is related to different groups. 

 For one thing it forms the fundamental support of the body-cells, which, 

 to a certain extent, are embedded in it. From it the finer and coarser 

 network, in which the lymph passes until it reaches the individual cells, 

 is formed. It is very questionable whether one is justified in assuming 

 that the cells of connective-tissue play a passive role here, or whether it is 

 not more probable that they take active participation in the exchange of 

 material between the blood and the lymph, and between the latter and 

 the remaining cells of the body. Its adjustment to purely mechanical 

 requirements is evident from the construction of the individual tissue; 

 for example, in the segregation of elastic fibers. A particularly differen- 

 tiated tissue, and one which also belongs in this group, is the fatty tissue; 

 the importance of which we have already considered. 



As regards the physiological functions of cartilage, but little is known 

 beyond its purely mechanical properties. It is, however, not to be doubted 

 that in it, as well as in body tissue, there is a constant occurrence of metabo- 

 lism. Growth never really ceases, for new cells are constantly being 

 formed. Numerous observations prove to us the dependence of the 

 metabolism in these organs upon the requirements placed upon them. 

 Their development ceases if for any reason there are no demands placed 

 upon them, and in such cases they retrogress even if they are already 

 well developed. The influence of the thyroid gland and other organs upon 

 growth, we have already mentioned. Very active metabolic processes 

 unquestionably take place in cartilage and bony tissue of the growing 



1 Blumenreich and Jacoby : Z. Hygiene u. Infectionskrankh., 29, 419 (1898). G. Jawein: 

 Virchow's Arch. 161, 461 (1900). 



