202 R. G. WESTALL 
concentrations of this amino acid. In the dog, rat and mouse the excretion pattern 
is dominated by taurine. 
Cerebrospinal Fluid. The amino acid concentration in cerebrospinal fluid (C.S.F.) 
is much lower than in blood plasma as can readily be seen in the chromatogram illus- 
trated in Fig. 3 when compared with that of plasma (Fig. 1) using a 625-1 sample in 
Leu 
nty 
VAL 
AA a ser 
GLU-NH, Sty 
Glu 
LYS 
Fig. 3. A paper chromatogram of normal human cerebrospinal fluid (625 jl). 
each case. Glutamine stands out as the most conspicuous spot and it is present in 
about the same concentration as in plasma. From investigations carried out by a 
number of workers**~*! it is apparent that most, if not all, of the amino acids which 
occur in blood can be found in C.S.F. although in a lowered concentration. This 
cannot mean that the C.S.F. derives its amino acids from the blood by passive diffusion 
through the blood-brain barrier as the two amino acid patterns are quite different. 
That the pattern should be usefully different is perhaps not surprising since the C.S.F. 
serves as a fluid medium for predominantly neurological tissues with their very 
different metabolism. For instance, GABA which is abundantly found in brain?? is 
often present in C.S.F. whereas it can be barely detected in the blood. So far, 
References p. 217/219 
