20 



PHYSIOLOGY. 



obtained by stirring blood as it is flowing, or by washing a clot in 

 clean water so as to dissolve out the colouring matter. 



Fibrine is white, sohd, flexible, and slightly elastic ; insoluble in 

 water, alcohol, and acids, but soluble in caustic potassa. Chemically 

 speaking, fibrine does not differ essentially from albumen. Phy- 

 siologically, the great variation lies in the spontaneous coagulation 

 of the fibrine, and when coagulated it is found to possess a definite 

 fibrous arrangement, the fibres crossing each other in every direction. 

 Fibrine is the plastic element of the blood, and with the serum 

 constitutes the liq. sanguinis ; it forms the huffy coat of the blood, 

 and is found in those exudations which take place either in inflam- 



mation, or from a peculiar 

 Fig. 2. formative action, destined to 



repair an old tissue, or pro- 

 duce a new one ; under these 

 circumstances, it is often called 

 coagulable lymph. (Fig. 2.) 

 Caustic potassa, carb. potass., 

 chloride of sodium, and many 

 neutral salts, when mixed with 

 blood, will prevent the coagu- 

 lation of fibrine. 



Casehie has many proper^ 

 ties in common with albumen 

 and fibrine. It exists in great- 

 est abundance in milk, and is 

 the basis of cheese. Its occurrence in other fluids has not been 

 positively detected. It may be obtained by allowing milk to remain 

 at rest till it is coagulated, skimming off" the cream, then washing 

 and drying the clot. 



Caseine is very perfectly coagulated by the action of rennet. 

 This coagulating power is not due to the acid of the stomach, but to 

 the pepsine resident in it. It is not coagulable by heat, but is readily 

 precipitated by the addition of an acid. It contains sulphur, but no 

 phosphorus. « 



Proteine. — If albumen, fibrine, or caseine, be dissolved in caustic 

 potassa, and acetic acid be added to the solution, a precipitate takes 

 place of a translucent, gelatinous material. This substance was 

 called proteine by Mulder, the discoverer, because it was supposed 

 to be the starting point or basis of all the tissues (from -t^wtsuw, I 

 take the first place). 



The precipitate is the same no matter which of the substances 

 above named be taken, be it animal or vegetable. They are looked 

 upon therefore as modifications of proteine by the addition of certain 

 proportions of phosphorus or sulphur, or both. 



Dried proteine is a hard, brownish-yellow substance, without taste, 



