6 Introduction to Animal Morphology. 



In the simplest animals the protoplasm is homo- 

 geneous, but in the more complex the homogeneous 

 yelk protoplasm becomes differentiated in development, 

 and thus we find cells whose contents vary. It has 

 been supposed that protoplasm may be a compound 

 albuminoid resolvable into its elements (myosin, neurin, 

 &c.) in the course of growth ; at least two substances 

 may be identified in it, one of which is active and 

 dilates on dilution with water, while the other is not.* 

 All cells are at first protoplasmic, whatever their ulti- 

 mate contents may be, and protoplasm seems to 

 possess the sum of the properties of the active cells 

 (muscle and nerve) derived therefrom. The chief ma- 

 terials derived from protoplasm in animals I have 

 appended in a note.f 



To complete our introductory studies, it may be 



pus cells within epithelial is more probably a case of wandering (Stcudder 

 and Volkmann}. 



* Heidenhain and Brucke suppose some cells to have a lacunary 

 structure, with a basis of a more solid albuminoid and a more fluid proto- 

 plasm contained therein. 



f Protoplasm derivates are of two kinds, Nitrogenous and non- 

 Nitrogenous. The first are : 



Albumen, CTsHnoNisSO^HgO, soluble in water, not precipitable by 

 alkaline carbonates nor sodium chloride, but is by heat. It varies in pro- 

 perty according to its source. Seralbumen (from blood serum) is not 

 coagulated slowly by ether. Ovalbumen is, and when injected under the 

 skin of an animal, speedily appears in the urine, which the other does not. 

 The ovalbumen of Raptorial birds is with difficulty coagulated by heat or 

 acid (Fr&my and Valenciennes). In some swimming birds and reptiles the 

 ovalbumen, when diluted, is slowly coagulated by heat. 



Globulin is insoluble in water, soluble in sodium chloride, coagulated 

 by heat, changed into acid albumen or syntonin by HC1 ; varieties of it are 

 Vitcllin, not precipitable by NaCl, when added in substance to saturate 

 its solution ; Myosin is thus precipitable. Paraglobulin or Fibrinoplastin^ 

 when combined with another albuminoid fibrinogen, forms fibrin, as in the 

 coagulation of blood. 



