FAT AND PHOSPHATIDES. 557 



Lactic acids may be detected in organs and tissues in the following 

 manner: After complete extraction with water, the protein is removed 

 by coagulation at boiling temperature and the addition of a small quan- 

 tity of sulphuric acid. The liquid is then exactly neutralized, while 

 boiling, with caustic baryta, and then evaporated to a syrup after filtra- 

 tion. The residue is precipitated with absolute alcohol, and the pre- 

 cipitate completely extracted with alcohol. The alcohol is entirely 

 distilled from the united alcoholic extracts, and the neutral residue is 

 shaken with ether to remove the fat. The residue is dissolved in water 

 and phosphoric acid added, and the solution repeatedly shaken with fresh 

 quantities of ether, which dissolves the lactic acid. The ether is now 

 distilled from the united ethereal extracts, the residue dissolved in water, 

 and this solution carefully warmed on the water-bath to remove the last 

 traces of ether and volatile acids. A solution of zinc lactate is prepared 

 from this filtered solution by boiling with zinc carbonate, and this is 

 evaporated until crystallization commences, and is then allowed to stand 

 over sulphuric acid. An analysis of the salts is necessary in careful 

 work. In regard to methods for the detection and quantitative estima- 

 tion of lactic acid we must refer to larger hand-books and to the work 



Of JERUSALEM. 1 



Fat is never absent in the muscles. Some fat is always found in the 

 intermuscular connective tissue; but the muscle-fibres themselves also 

 contain fat. The quantity of fat in the real muscle substance is always 

 small, usually amounting to about 10 p. m. or somewhat more. A 

 considerable quantity of fat in the muscle-fibres is found only in fatty 

 degeneration. A part of the muscle-fat can be readily extracted, while 

 another part can be extracted only with the greatest difficulty. This 

 latter part, it is claimed, exists finely divided in the contractile sub- 

 stance itself and is richer in free fatty acids, standing, according to 

 ZUNTZ and BoGDANow, 2 in close relation to the activity of the muscles 

 because it is consumed during work. Lecithin is a regular constituent 

 of the muscles, and it is quite possible that the fat which is difficult of 

 extraction and which is rich in fatty acids depends in part on a decom- 

 position of the lecithin and the phosphatides. ERLANDSEN has shown, 

 that phosphatides of various kinds occur in the muscles and indeed different 

 quantities in different muscles. According to him the ox-heart muscle 

 is richer in phosphatides than the muscle of the thigh, and RUBOW 3 

 claims that the heart of the dog is richer in phosphatides than the striated 

 muscle. ERLANDSEN found lecithin and diamino-phosphatide in the 

 heart as well as the thigh-muscle, while the monoamido-phosphatide 

 cuorin, which occurs abundantly in the heart, is found as traces in the 

 thigh-muscle. 



1 Bioch. Zeitschr., 12. 



2 Arch. f. (Anat. u.) Physiol., 1897. e 



3 Erlandsen, Zeitschr. f. physiol. Chem 51; Rubow, Arch. f. exp. Path. u. Pharm., 

 52. 



