ALBUMINATES AND OTHER PROTEIDS. 377 



cent, solution of sodium or ammonium chloride, it yields a viscid fluid which, when dropped 

 into a large quantity of distilled water, gives a white flocculent precipitate of myosin. It 

 is also precipitated from its NaCl solution by crystals of NaCl. For Kuhne's and other methods 

 see 293. 



(6) Globin (Preyer), the proteid residue of haemoglobin ( IS). 



Class III. Derived Albumins (Albuminates). (1) Acid-albumin or Syntonin. When pro- 

 teids are dissolved in the stronger acids, e.g., hydrochloric, they become changed into acid- 

 albumins. They are precipitated from solution by the addition of many salts, sodic chloride, 

 acetate or phosphate, or by neutralisation with an alkali, e.g., sodic carbonate, but they are not 

 precipitated by heat. The concentrated solution gelatinises in the cold, and is redissolved by 

 heat. Syntonin, which is obtained by the prolonged action of dilute hydrochloric acid (2 per 

 1000) upon minced muscle, is also an acid-albumin. It is formed also in the stomach during 

 digestion ( 166, I.). According to Soyka, the alkali- and acid-albumins differ from each other 

 only in so far as the proteid in the one case is united with the base (metal) and in the other 

 with the acid. 



(2) Alkali-albumin. If egg- or serum-albumin be acted upon for some time by dilute 

 alkalies, a solution of alkali-albumin is obtained. Strong caustic potash acts upon white of 

 egg, and yields a thick jelly, Lieberkuhn's jelly. The solution is not precipitated by heat, but 

 it is precipitated by the addition of an acid. [Although alkali-albumin is precipitated 

 on neutralisation, this is not the case in the presence of alkaline phosphates, e.g., sodic 

 phosphate. ] 



(3) Casein is the chief proteid in milk ( 231). It is precipitated by acids and by rennet at 

 40 C. In its characters it is closely related to alkali-albuminate, but it contains more N. It 

 contains a large amount of phosphorus (0*83 per cent.). It may be precipitated from milk by 

 diluting it with several times its volume of water and adding dilute acetic acid, or by adding 

 magnesium sulphate crystals to milk and shaking vigorously. Owing to the large amount of 

 phosphorus which it contains, it is sometimes referred to the nucleo-albumins. When it is 

 digested with dilute HC1 (0*1 per cent.) and pepsin at the temperature of the body, it gradually 

 yields nuclein. 



Class IV. Fibrin. ( 27) and for the fibrin-factors ( 29). 



Class V. Peptones. For peptones and propeptone or the albumoses ( 166, I.) ; in urine 

 ( 264). 



Class VI. Lardacein and Other Bodies. There fall to be mentioned the "yelk-plates," 

 which occur in the yelk : Ichthin (cartilaginous fishes, frog) ; Ichthidin (osseous fishes) ; 

 Ichthulin (salmon) ; Emydin (tortoise) ; also the indigestible amyloid substance or lardacein, 

 which occurs chiefly as a pathological infiltration into various organs, as the liver, spleen, 

 kidneys, and blood-vessels. It gives a blue with iodine and sulphuric acid (like cellulose), and 

 a mahogany-brown with iodine. It is difficult to change it into an albuminate by the action of 

 acids and alkalies. 



Class VII. Coagulated Proteids. When any native albumins or globulins are coagulated, 

 .g., at 70 C, they yield bodies with altered characters, insoluble in water and saline solutions, 

 but soluble in boiling strong acids and alkalies, when they are apt to split up. They are dis- 

 solved during gastric and pancreatic digestion to produce peptones. 



Appendix : Vegetable Proteid Bodies. Plants, like animals, contain proteid bodies, 

 although in less amount. They occur either in solution in the juices of living plants or in the 

 solid form. In composition and reaction they resemble animal proteids. 



[The characters of vegetable proteids have a great resemblance to animal proteids. They 

 have frequently been obtained in a crystalline form, e.g., from the seeds of the gourd and various 

 oleaginous seeds. They occur in greatest bulk in the seeds of plants, aleurone grains being for 

 the most part composed of them. In seeds, globulins and "vegetable peptone" form the 

 greater proportion of the proteid constituents. ] 



[Globulins. These varieties have been described as occurring in the seeds of plants: 

 vegetable myosin, vitellin, and paraglobulin (Martin). They have practically the same pro- 

 perties as those found in the animal kingdom : vegetable vitellin has, however, not been suffi-* 

 ciently studied. Paraglobulin has been found in papaw juice (Martin). Myosin occurs in the 

 seed of leguminosae, in flour, and in the potato.] 



[Albumin. The existence of a body corresponding to egg- or serum-albumin in the vege- 

 table kingdom is doubtful (Ritthausen). Such a body has been described in papaw juice 

 (Martin).] 



[Vegetable Peptone : Albumoses. A true peptone has not yet been recognised in plants : 

 what has been described as such is hemi-albumose ( Vines). Albumoses have been found in the 

 seeds of leguminosee, in flour, and in papaw juice. In the last, two forms occur, called respec- 

 tively a- and 0- phytalbumose. The former, o-phytalbumose, agrees with the hemi-albumose 

 described by Vines, being soluble in cold and boiling water ; giving also a biuret-reaction, and 

 a precipitate by saturation with sodium chloride only in an acid solution. The latter, /8-phytal- 

 bumose, is soluble in cold, but not in bqiling, distilled water ; hence it is precipitated by heat. 



