416 FIRST CLASS OF MINERAL CONSTITUENTS. 



ulated, is precipitated with it, even when there is a sufficient quan- 

 tity of free acid in the fluid. Chondrin, according to Mulder, yields 

 on incineration 4*09^ of ash, most of which is phosphate of lime. 

 As chemical compounds of phosphate of lime with albumen and 

 with gelatin have been prepared, which contain much greater quan- 

 tities of this salt (in albumen even one -third) there would be nothing 

 absurd in the supposition that a portion of the phosphate of lime 

 contained in the bones, is chemically combined with the cartila- 

 ginous substance, even though it may be removed by hydrochloric 

 acid. 



The constant occurrence of phosphate of lime in the histoge- 

 netic substances, and especially in the plastic fluids, as well as its 

 deposition in many pathologically degenerated cells of the animal 

 body, obviously strengthen the opinion that this substance plays an 

 important part in the metamorphosis of the animal tissues, and es- 

 pecially in the formation and in the subsequent changes of animal 

 cells. This subject must, however, be more fully investigated,, 

 before we can draw any definite conclusions regarding it. 



In connexion with this subject, C. Schmidt* has, however, 

 made a very interesting observation regarding the folds of the 

 mantle of Unio and Anodonta. They consist of a middle layer of 

 fibres of areolar tissue, which on its inner side is covered with 

 ciliated epithelium and towards the shell with glandular epithelium ; 

 in these parts he found about 15$ of phosphate of lime, 3 of car- 

 bonate of lime and soluble salts, and 82^ of organic matter, the 

 quantity of phosphate of lime being very extraordinary, as the 

 blood of these animals contains only 0*034^ of this salt. The 

 mucus, lying between the shell and the mantle of these animals, 

 and secreted by the layer of glandular cells on the mantle for the 

 consolidation of the shell, consists of a strong basic albuminate of 

 lime containing only a little preformed carbonate of lime. Schmidt 

 is of opinion that the function of this glandular epithelium, which 

 resembles the cells of the liver, is to secrete from the blood 

 a combination of albumen and lime, decomposable by the carbonic 

 acid of the air or of water, for the formation of the shell, while it 

 leaves the phosphate of lime for those organs which require it for 

 the process of cell-formation (the testicle and ovary.) 



The questions now arise, how do such masses of phosphate 

 of lime find their way into the animal body ? Or how are 

 they formed in it ? That carnivorous animals receive a more 

 than sufficient quantity with their food is obvious from the prece- 

 ding observations. Graminivorous animals likewise receive in their 



* Zur vergleiclienden Physiol. S. 56-60. 



