HYDROLYTIC FERMENTS. 379 



5. Spongin, allied to fibroin, occurs in the bath-sponge, and yields, as decomposition pro- 

 ducts, leucin and glycin (Stadeler). 



6. Elastin, the fundamental substance in elastic tissue, is soluble only when boiled in con- 

 centrated caustic potash C 55-55*6, H 7*1-77, N 16*1-177, 19-2-21 : 1 per cent. It yields 

 36 to 45 per cent, of leucin and ^ per cent, of tyrosin. 



7. Gelatin (Glutin), obtained from connective-tissues by prolonged boiling with water ; it 

 gelatinises in the cold C 52-2-507, H 6-6-7*2, N 17*9-18-8, S + O 23'5-25 (S 0*7 per cent.). 

 [The ordinary connective-tissues are supposed to contain the hypothetical anhydride collagen, 

 while the organic basis of bone is called ossein.] It rotates the ray of polarised light strongly 

 to the left= - 130. By prolonged boiling and digestion, it is converted into a peptone-like 

 body (gelatin-peptone), which does not gelatinise ( 161, I.). [It swells up, but does not dis- 

 solve in cold water ; when dissolved in warm water, and tinged with Berlin blue or carmine, it 

 forms the usual coloured mass which is employed by histologists for making fine transparent 

 injections of blood-vessels.] A body resembling gelatin is found in leuksemic blood and in 

 the juice of the spleen ( 103, I.). When decomposed with sulphuric acid it yields glycin, 

 ammonia, leucin. but no tyrosin. [It is precipitated from its solution by alcohol, mercuric 

 chloride, metaphosphoric acid, phospho-wolframic acid, taurocholic acid, tannic acid, but the 

 precipitate with the last does not occur when salts are absent. It is readily soluble in dilute 

 acids, even in acetic acid. When boiled with Millon's reagent, it is not coloured red. With 

 cupric sulphate and caustic soda it gives a violet colour which, on boiling, becomes light red. 

 It gives no colour with concentrated H 2 S0 4 and acetic acid.] 



8. Chondrin occurs in the matrix of hyaline cartilage and between the fibres in fibro-cartilage. 

 It is obtained from hyaline cartilage and the cornea by boiling. [Its solutions gelatinise on 

 cooling.] It occurs also in the mantle of molluscs C 49*5-50-9, H 6-6-7-1, N 14 '4-14*9, S + O 

 27*2-29 (S 0*4 per cent.). When boiled with sulphuric acid it yields leucin ; with hydrochloric 

 acid, and when digested, chondro-glucose (Meissner) ; it belongs to the glucosides, which con- 

 tain N. When acted upon by oxidising reagents it is converted into gelatin (Brame). The 

 substance which yields chondrin is called chondrogen, which is perhaps an anhydride of chon- 

 drin. The following properties of gelatin and chondrin are to be noted : Gelatin is precipi- 

 tated by tannic acid, mercuric chloride, chlorine water, platinic chloride, and alcohol, but not 

 by acids, alum, or salts of silver, iron, copper, or lead ; its specific rotation is = - 130. [Com- 

 pare these precipitants with those of albumin.] Chondrin is precipitated by acetic acid and 

 dilute sulphuric and hydrochloric acids, by alum, and by salts of silver, iron, and lead ; its 

 specific rotation = -213. 



9. The hydrolytic ferments have recently been called enzymes by W. Kiihne, in order to 

 distinguish them from organised ferments, such as yeast. The enzymes, hydrolytic or organic 

 ferments, act only in the presence of water. They act upon certain bodies, causing them to 

 take up a molecule of water. They all decompose hydric peroxide into water and O. They are 

 most active between 30 to 35 C, and are destroyed by boiling, but when dry they may be 

 subjected to a temperature of 100 without being destroyed. Their solutions, if kept for a long 

 time, gradually lose their properties and undergo more or less decomposition. 



(a) Sugar-forming or diastatic-ferment occurs in saliva ( 148), pancreatic juice ( 170), 

 intestinal juice ( 183), bile ( 180), blood ( 22), chyle ( 189), liver ( 174), in human milk 

 ( 231). Invertin in intestinal juice ( 183). Almost all dead tissues, organic fluids, and even 

 proteids, although only to a slight degree, may act diastatically. Diastatic ferments are very 

 generally distributed in the vegetable kingdom. 



(b) Proteolytic, or ferments which act upon proteids. Pepsin in gastric juice and in muscles 

 ( 166), in vetches, myxomycetes (Krukenberg), trypsin in the pancreatic juice ( 170), a similar 

 ferment in the intestinal juice ( 183), and urine ( 264). 



(c) Fat-decomposing in pancreatic juice ( 170), in the stomach ( 166). 



(d) Milk-coagulating in the stomach ( 166), pancreatic juice ( 170), and perhaps also in the 

 intestinal juice (?) ( W. Roberts). 



[The importance of fermentative processes has already been referred to in detail under 

 " Digestion." Ferments are bodies which excite chemical changes in other matter with which 

 they are brought into contact. They are divided into two classes : 



(1) Unorganised ; soluble or non-living. 



(2) Organised, or living.] 



[(1) The Unorganised Ferments are those mentioned in the following table. They seem to be 

 nitrogenous bodies, although their exact composition is unknown, and it is doubtful if they 

 have ever been obtained perfectly pure. They are present in many secretions, and are produced 

 within the body by the vital activity of the protoplasm of cells. They are termed soluble 

 because they are soluble in water, glycerin, and some other substances ( 148), while they can 

 be precipitated by alcohol and some other reagents. They do not multiply during their 

 activity, nor is their activity prevented by a certain proportion of salicylic acid. They are 

 not affected by oxygen subjected to the compression of many atmospheres (P. Bert). They are 

 non-living. Their other properties are referred to above.] 



