CHAPTER VI. 



CRYSTALLIZABLE NITROGENOUS MATTERS. 



THE fifth and last group of proximate principles consists of a 

 number of colorless substances which, like the albuminous matters, 

 contain nitrogen, but which differ from them in being readily crystal- 

 lizable. Many of them are evidently derived from the albuminous 

 ingredients of the body by retrograde metamorphosis, being dis- 

 charged from the system as products of excretion. Others do not 

 exhibit this character, and are found only in the permanent tissues or 

 the internal fluids of the body. Several of them are of comparatively 

 recent discovery, and, although undoubtedly of importance in the con- 

 stitution of the body, are still somewhat obscure in their physiological 

 relations. 



Lecithine, C 44 H 90 NP0 9 , 



From Af'xt^oj, the yolk of egg, in which substance it was first discovered. 

 Lecithine was for some time described under the name of phosphorized 

 fat, owing to the circumstance that one of the products of its de- 

 composition is phosphoglyceric acid (C 3 H 9 P0 6 ). It is not, however, 

 a fatty substance, since it contains nitrogen, and in other respects 

 differs from the fats. As mingled or combined with other animal mat- 

 ters, it has also been known by the name of " protagon." Lecithine is 

 of very wide distribution in both the animal and vegetable kingdoms, 

 occurring in the cereal grains and the leguminous seeds, and, according 

 to Hoppe-Seyler, in the cellular juices of a variety of plants. It is 

 found in the blood, both in the plasma and the globules, in the bile, the 

 spermatic fluid, the yolk of egg, and particularly in the tissues of the 

 brain, spinal cord, and nerves. In the plasma of the blood, it is in the 

 proportion of 0.4 part per thousand, and in the fresh substance of the 

 calf's brain, according to the analyses of Petrowsky, 1 in the proportion 

 of 31 parts per thousand. Taking into account the watery ingredients 

 of the brain, lecithine is about equally abundant in the white and gray 

 substance ; but of the solid matters alone, it constitutes a little less than 

 10 per cent, in the white substance, and rather more than It per cent, 

 in the gray substance. 



Lecithine obtained from either of these sources, if treated with water, 

 swells up into a pasty mass and gives origin to the remarkable appearances 

 under the microscope known as "myeline forms;" that is, a great 



1 Archiv fur die gesammte Physiologie, 1873, Band vii. p. 101. 

 (102) 



