ALBUMINOUS SUBSTANCES OR PROTEIDS. 343 



soluble in water, alcohol, and ether, but swells up and dissolves 

 slowly in diluted acids. 



Whether or not fibrin exists as such in the blood, or is pro- 

 duced by the decomposition of another substance when blood 

 leaves the organism, is a question not yet decided; it is, how- 

 ever, highly probable that there exist in the blood two sub- 

 stances, known as paraglobulin and fibrinogen, which combine 

 together (forming fibrin) as soon as the blood leaves the or- 

 ganism. 



Muscle-fibrin or muscle-protoplasm is a liquid contained in the 

 muscles; after death this liquid coagulates, becomes solid (rigor 

 mortis), and this insoluble body is termed myosin or Jlesh-Jibrin. 



Vegetable fibrin or gluten exists in many parts of vegetables, 

 and is best obtained from wheat-flour by kneading it on a sieve 

 with water, when the starch passes through and gluten remains 

 as a soft, elastic mass, insoluble in water, alcohol, and ether. It 

 is probably a mixture of several proteids. 



Milk-casein, most likely an alkali-albumin, is the principal 

 albuminous substance of milk, in which it occurs in solution. 



Casein is precipitated by acids, alcohol, many metallic salts, 

 and by rennet; it is soluble in alkalies. 



Vegetable casein or legumin occurs in considerable quantities 

 in the seeds of leguminosae, such as peas and beans, which 

 contain nearby 25 per cent.; it is also found in almonds, 

 various nuts, etc. It shows reactions very similar to milk- 

 casein. 



Peptone is a term assigned to the products formed by the 

 action of gastric and pancreatic juices upon proteids during the 

 process of digestion. Peptones are soluble in water, insoluble 

 in alcohol; the neutral aqueous solution is precipitated by 

 alcohol, but not by heat, acids, or alkalies. Peptones are capa- 

 ble of dialysis, or of diffusion through membranes, whilst pro- 

 teids are not. Whilst peptones are looked upon as but slightly 

 altered albumins by some scientists, they are considered by 



