238 TRANSACTIONS OF THE [JUNE 4, 
trate. Otherwise the strong alcohol would precipitate the sul- 
phate in the tissues. 
In the two first mentioned mixtures a precipitate, probably 
of silver sulphate, formed. To avoid this waste it would be well 
to reduce the strength of either the sodium sulphate or silver 
nitrate Zine sulphate seemed to produce results similar to the 
sodium salt, but could be mixed in larger proportions with the 
silver solution without forming a precipitate. 
In certain cases this modification gave very good results. It 
is, however, not always necessarily an improvement, and further 
experience is requisite to determine its exact value. 
2. Lithium Bichromate Method. 
It is, however, another modification to which I wish at pres- 
ent to call especial attention and which will, I think, prove val- 
uable in certain lines of work. 
While embryonic tissue is necessary to obtain good results in 
the demonstration of the course, ramification and terminations 
of the nerve fibres, their relations to the cells and to each other, 
etc., the investigator often simply wishes to ascertain the forms, 
including the protoplasmic processes, arrangement, ete., of the 
cells themselves in the central nervous system, and is, moreover, 
limited to adult material. This is often the case, for example in 
medical work, especially that upon the pathology of the brain. 
It is in such work upon the adult brain that the rapid method, 
owing to the employment of osmic acid, which tends to over- 
harden, yields its poorest results. 
This, together with the expense of the osmic acid, may be 
avoided by the use of the long Golgi method, which dispenses 
with the osmic acid, or by one of the sublimate methods. Both 
of these, howeyer, have the disadvantage of requiring a consid- 
able period of time, from about a month upwards, while the 
long silver method is also uncertain and the sublimate does not 
appear to give the same delicacy of impregnation as the former. 
I have found that the period of time necessary to reach the 
proper degree of hardening for impregnation may be reduced 
from the 20-30 days or so required by the long method to from 
1-3 days by simply using lithium bichromate instead of potas- 
sium bichromate. 
This does not do away with the uncertainty, for the tissue 
passes through the favorable period quite rapidly, apparently, 
but it has the advantage of reducing it and the whole process to 
such a short period of time that the trouble and delay are very 
materially lessened. The tissue should be cut into small pieces 
and put into a liberal supply of a 2-3% solution of lithium bi 
