APPENDIX. 683 
that rotates the plane of polarized light, the free acid being dextro-ro- 
tatory. 
The Bibasic Acids (C,H. _ 0.) of the Oxalic Series. 
Only a few members of this series are of special interest to the medi- 
cal chemist. 
Oxalic acid. C2H20.,(CO2H)e. 
Does not occur free in the mammalian body, but is normally present 
in small quantity as an oxalate, chiefly of calcium, in the urine of most 
mammals. In certain disordered states of the metabolism it occurs in 
the urine of man in characteristic dumb-bell forms, in regular octahedra, 
or in square columns with pyramidal ends. These are insoluble in 
water, alcohol, ether, ammonia, and acetic acid, but readily dissolve in 
hydrochloric acid. 
Succinic acid. C.H.(CO.H)s. 
Occurs in the spleen, thymus and thyroid bodies, and in hydrocele 
and hydrocephalic fluids. It crystallizes in large rhombic tablets, and 
more rarely in prisms; sparingly soluble in water. 
Complex NitRoGENoUs FATS. 
The bodies to be described in this chapter may most of them be ex- 
tracted from the nerves and nervous centers. 
Lecithin. C.HooNPOs. 
This substance may be obtained from diverse sources—the blood, bile, 
serous fluids, and especially from the brain, nerves, yelk of egg, semen, 
pus, the colorless corpuscles, and even the electrical organ of fishes. It 
may be separated as a white, somewhat crystalline, soft body, soluble in 
cold alcohol, more so in hot alcohol, in ether, chloroform, fats, benzol, 
ete. 
Glycerinphosphoric acid. CsH»POs. 
May arise as a decomposition product of lecithin, thus: 
CasHooNPOo + 3H20 = 2CieHseO2 + CsHePOc + CsHisNOs. 
Lecithin. Stearic acid. Glycerin phos- Neurin. 
phoric acid. 
Protagon. CisoHsoeNsPOss (2). 
The formula of most of these bodies is doubtful, and especially is this 
remark true of protagon. This body is insoluble in cold water, but 
swells in it like gelatin. At 200° C. it melts to a sirup. There has 
been much discussion as to whether it is a single body, or a mixture of 
lecithin and cerebrin. It is derivable from the brains of mammals. 
Neurin. C:H:sNOsz. 
It is a very unstable body, difficult to get or keep in a free state, It 
has been obtained from bile; hence the name cholin. 
Cerebrin. C,;HssNOs (2). 
Abounds in the brain in the axis cylinder of nerves and in pus-cor- 
puscles. It may be obtained as a colorless hygroscopic powder. 
