Proceedings of the Association of American Anatomists XV 
nervous system and the organs of sense in mammals. This is in accord 
with the findings of glycogen in the cells of the spinal cord of Amphioxus 
and Asymmetron and in the brain and cochlear canal of Ammoccetes 
which were reported last year (American Journal of Anatomy, Vol. IV, 
p. XII of Proceedings of Association of American Anatomists). 
AN EXAMINATION OF THE METHODS FOR THE MICHROCHEMICAL 
DETECTION OF PHOSPHORUS IN TISSUES. By Roserr R. BENSLEY. 
Hull Laboratory of Anatomy, University of Chicago. 
’ 
Experiments were described which seemed to show that the results ob- 
tained by the method of Macallum are in reality due to the formation of 
molybdie acid compounds with the tissue-substances. The reasons for 
this conclusion are briefly as follows: t 
Phenylhydrazin hydrochloride reacts with solutions of molybdic acid 
prepared by the methods of Ullik and Graham to produce the blue oxide 
of molybdenum. Sections treated with solutions of molybdic acid con- 
taining 5% of nitric acid, then reduced by a solution of phenylhydrazin 
hydrochloride, give a reaction similar in all respects to the so-called 
phosphorus reaction, except that a strong reaction is obtained in the col- 
lagenic fibrils as well as in the nuclear chromatin. 
Nitric acid affects the reduction of molybdic acid, ammonium molyb- 
date and ammonium phosphomolybdate by phenylhydrazin hydrochloride 
in the same way, but to different degrees, inasmuch as low concentrations 
of nitric acid serve to prevent the reduction of molybdic acid and of am- 
monium molybdate to the blue oxide, while high concentrations (e. g. 
36%) of nitric acid only retard the reduction of ammonium phosphomo- 
lybdate. Accordingly, solutions of phenylhydrazin hydrochloride con- 
taining a high percentage of nitric acid should detect ammonium phos- 
phomolybdate in sections, while not affecting in any way molybdic acid 
compounds or ammonium molybdate mechanically held by the tissue. 
Tests made on sections impregnated with molybdic acid and on sections 
into which ammonium phosphomolybdate has been artificially introduced 
show that this is the case. Sections treated with molybdic acid solutions 
show no reaction with solutions of phenylhydrazin hydrochloride con- 
taining a low percentage of nitric acid, while sections treated with phos- 
phorie acid solutions and then with warm nitric molybdate reduce rapidly 
in a solution containing 0.1% of phenylhydrazin hydrochloride and 15% 
of nitric acid. Sections treated with Macallums’s nitric-molybdate re- 
agent behave like sections treated with solutions of molybdie acid. That 
is to say, low concentrations of nitric acid suffice to prevent their reduc- 
tion by phenylhydrazin hydrochloride. For example, a solution contain- 
