CHAP, xi THE ALBUMINOIDS 553 



have the same percentage composition, and give the same colour- 

 reactions as do other albumins. 



It must, however, be admitted that the anatomical relationship 

 conditions a series of chemical peculiarities which are common to all 

 albuminoids. As their function is to act as supporting structures and 

 coverings to the body, and to impart to the living organo-plasm shape 

 and adhesiveness, they all possess the physical property of great firm- 

 ness. Thus the extraordinary hardness of the bones of vertebrates, 

 or of the shells of molluscs, or of other integumental structures acting 

 as a protection to many lower animals, is due to albuminoids forming 

 -an organic ground-matrix, which subsequently becomes impregnated 

 with mineral matter. In other cases we have to deal with unyielding 

 tissues possessed of great toughness as in tendons, or with elastic 

 bands as in the ligamentum nucha3, or with loosely arranged tissues 

 possessing a certain degree of toughness, as in the areolar tissues. In 

 this last case, however, the looseness is simply due to a looser arrange- 

 ment of the same white fibrous tissue as is met with in tendons. 

 " The essential feature of all connective tissues is that they must be 

 completely insoluble in all animal juices " (Cohnheim). The author 

 must differ from Cohnheim, as he has ample experimental evidence 

 showing this view to be incorrect, for the connective tissues all over the 

 body and including the bones are diminished during inanition, i.e. are 

 partly converted into ' circulating proteid.' 



All albuminoids are quite insoluble in water and in salt solutions, 

 and are also hardly soluble in dilute acids or alkalies. To get them, 

 therefore, into solution one requires to use means by which their 

 fundamental rigid character is destroyed, and this cannot be done 

 without at the same time destroying, or at least chemically altering 

 these albuminoids. As a chemical substance cannot be properly 

 examined except it be in solution, it follows that it is impossible to 

 examine albuminoids in their natural state, and that in getting them 

 into solution we have to subject them to a good many changes. For 

 these reasons it is even more difficult to isolate albuminoids and to 

 define their chemical individualities, their properties, and compositions 

 than it is in the case of the cell-albumins, for these occur, in the cell- 

 plasm, at least in a semi-fluid state. Most of the investigations into 

 the albuminoids date back a long time or are quite recent. The 

 middle period of investigations into the chemistry of albumins being 

 especially concerned with the study of the solubilities of albumins took 

 no notice of the albuminoids. 



A comparison of the more physical properties of the native, firm 

 albuminoids, with those of the colloidal albumins is not well possible. 



