CHAPTER VI. 

 CRYSTALLIZABLE NITROGENOUS MATTERS. 



THE fifth and last group of bodily ingredients consists of a number 

 of colorless substances, which resemble the albumenoids in con- 

 taining nitrogen, but differ from them in being crystallizable. Many 

 of them are evidently derived from the albumenoids by retrograde 

 metamorphosis, being discharged from the system as products of excre- 

 tion. Others do not exhibit this character, and are found only in the 

 permanent tissues or the internal fluids. Several of them, though 

 undoubtedly of importance in the constitution of the body, are still 

 obscure in their physiological relations 



/ 



1. Lecithins, C 4t H 90 NPO 9 , 



From AEX&O;, the yolk of egg, in which substance it was first discovered. 

 Lecithine was formerly described under the name of phosphorized fat, 

 owing to the circumstance that one of the products of its decomposition 

 is phosphogly eerie acid (C 3 H 9 PO 6 ). It is not, however, a fatty sub- 

 stance, since it contains nitrogen, and otherwise differs from the fats. 

 As mingled or combined with other animal matters, it has also been 

 known by the name of "protagon." Lecithine is of very wide dis- 

 tribution in both the animal and vegetable kingdoms, occurring in the 

 cereal grains and 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 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,* 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 17 per cent, in the gray 

 substance. 



Lecithine obtained from either of these sources is an indistinctly 

 crystallizable substance, of waxy consistency, liquefying at a gentle 

 heat, readily soluble in alcohol, less so in ether, and to some extent in 

 chloroform and the fatty oils. If treated with water, it swells into 

 a pasty mass without dissolving, and gives origin, under the micro- 

 scope, to the appearances known as " myeline forms ; " that is, a great 



* Archiv fiir die gesammte Physiologic. Bonn, 1873, Band vii., p. 101. 



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