xo8 Physiology and its Chemistry [January, 
that there are questions to be solved which are further 
removed from the abilities of the untrained mind, and which 
demand for their elucidation means at the command of but 
few private individuals, is, we may say, notorious and ac- 
knowledged. We have endeavoured, en passant , to indicate 
some of these problems, and did space allow it would be 
matter of interest to allude to many others. A few may 
conveniently be here given. In the first place, of the 
matters entering into the composition of so-called extractives 
we know extremely little : in faCt, Liebig — who has worked 
at this qnestion more than any other man — was only suc- 
cessful in ascertaining the nature of less than 17 per cent 
of the total matter. Fortunately for science Liebig was 
more conscientious than many workers in this direction ; 
for it is a weakness not only on the part of the physiological 
chemist, but on that of the ordinary chemist, in their inves- 
tigations, to seize upon one particular product, preferably 
choosing the most crystalline, and to examine it to the 
negleCt of the 99 per cent. This would not be of so much 
import if at the same time it were accompanied by a state- 
ment of the faCt, but as it is, their publications are not 
rarely so worded as to convey to the mind of the reader, 
imperceptibly, the idea that nothing remains to be done. 
Again, with remarkably few exceptions, nothing is known 
regarding those relations which undoubtedly exist between 
the chemical constituents of the various organs, tissues, 
and juices of the body. We will refer for the moment, in 
illustration, to the identity* of the phosphorised principles 
accompanying blood corpuscles with one of the forms of 
myelin as existing in the brain. This discovery, however, 
is but the key-note to other discoveries which must and will 
be effected before we can even speculate on the functions of 
that matter itself, either in relation to the intellectual faculty 
or in regard to the blood function. That there are similar 
relations existing between other brain components and the 
bodies found in the liver and the urine, we have also no 
doubt, but the nature of these relations, or the connection 
of excretory products with the albuminous constituents of the 
body, is almost entirely hidden. But with the increase of 
our acquaintance with substances already known to Science, 
and with the discovery of greater numbers yet to be revealed, 
will come the explanation. The pursuit of this science, 
* “ On Hemine, Hematine, and a Phosphorised Substance contained in 
Blood Corpuscles.” By J. L. W. Thudichum and C. T. Ki^gzett. . Journ. 
Chem. Soc., New Series, No. 165, September, 1S76. 
