

1905.] Silver Reaction in Animal and Vegetable Tissues. 229 
Ill. General Remarks. 
The results given in the preceding pages make it quite clear that the 
reaction which animal and vegetable tissues give with nitrate of silver 
dissolved in dilute nitric acid may be attributed to halogens in haloid form,* 
and to taurine and creatine, and that proteids and gelatin do not, when freed 
from traces of haloids, give the slightest colour reaction with the reagent. Of 
the two organic compounds which give the colour reaction, taurine may be 
neglected, since it obtains in infinitesimal quantities in animal tissues, and 
creatine, although present to the extent of 0°21 to 0°39 per cent. in frog’s 
muscle, and of 0-4 per cent. in rabbit’s muscle,f occurs in inappreciable quan- 
tities in other organs and it is absent altogether from invertebrate tissues.{ 
One can, therefore, by appropriate selection of tissues of animal and vegetable 
forms for treatment with the reagent, determine, with a considerable amount 
of certainty and a very great degree of accuracy, the distribution of chlorides 
and, perhaps also, of other haloids, in various cytological elements. 
This determination has already been made in the case of a number of 
cellular structures, and the results which have been obtained are of very great 
interest. These will form the subject of another paper, but two of them, which 
stand out in special prominence, are that intercellular material and structures, 
including the so-called cement substance of Von Recklinghausen, are rich in 
chlorides, and that normal nuclei of animal and vegetable cells are absolutely free 
From them. 
* Compounds containing chlorine in a “ masked” form as, for example, trichloracetic 
acid, give the silver haloid and subhaloid reactions after several days only. 
+ F. Nawrocki, “ Ueber die quantitative Bestimmung des Kreatins in Muskeln,” ‘ Zeit. 
fiir anal. Chem.,’ vol. 4, p. 330, 1865. 
{ Krukenberg, ‘ Vergleichend-Physiologische Vortrage,’ p. 316, Heidelberg, 1886 ; also 
Krukenberg’s papers in ‘ Untersuchungen a. d. Physiol. Inst. d. Univ. Heidelberg,’ vols. 3 
and 4, 1880 and 1881. 
