69 
(hemolymph) of certain insects was made the subject of an investiga- 
tion by Krukenberg ( 254 ) and also by Fredericq ( 176 ) as early as 1881. 
According to Fredericq, oxygen was responsible for this change of 
color, whereas, according to Krukenberg, it was probably due to 
carbon dioxide. Fredericq also made the interesting observation 
that the blood obtained from insects which previous to bleeding had 
been heated to 50-55° C. for fifteen minutes, showed no blackening 
on exposure to the air. Dewitz ( 138 ) has also shown that an oxidase, 
the precise nature of which was not investigated, plays an essential 
role in the metamorphosis of certain insects. As is well known, the 
larvae of the fly are white during the entire life of this phase of the 
insect, and only at the moment of the formation of the pupa does any 
change of color take place. This color change begins in the abdominal 
cavity as two large colored spots. 
Biedermann ( 67 ) seems to have been the first to obtain evidence of 
tyrosinase of animal origin. In his experiments the middle intestine 
( Mitteldarme) of three or four starving meal worms ( Tenebria molitor) 
were placed in chloroform water. The light yellowish solution thus 
obtained was divided into two portions. To one portion a few drops 
of a solution of tyrosin was added, and both were kept over night in 
open watch glasses in a moist chamber. The portion containing the 
tyrosin had become violet black in color, whereas the portion to which 
no tyrosin had been added was only slightly darkened. 
Yon Furth and Schneider ( 179 ) have also made important contribu- 
tions to our knowledge of animal tyrosinase and its relation to 
animal pigmentation. The pupae of the butterfly, chiefly of the 
species Deiciphila elpenor and eupborbiae, furnished the material for 
their investigations. By careful puncture and squeezing, about 
one cubic centimeter of a clear, bright greenish-colored fluid was 
obtained from each pupa. This was the hemolymph, called for the 
sake of brevity the blood of the insect. Gn standing a few moments 
in the air this fluid began to darken on the upper surface, and after 
a time a black clot separated. On the other hand, if the proteid of 
the fresh blood be removed by boiling, it shows none of these color 
changes on standing in the air. When dried in vacuo over sulfuric 
1 acid, no change of color in the blood was observed. When a few 
drops of the fresh blood was added to a few cubic centimeters of a 
fresh solution of tyrosin, there appeared on the upper surface of the 
i solution a violet-colored ring; this color gradually spreads through 
the solution until the whole of it is colored a dark violet, and is turbid 
through the separation of a fine and coarse flocculent precipitate. On 
the other hand, two drops of the fresh blood added to water gave a 
solution which showed none of the color changes, but ultimately gave 
a precipitate scarcely darker in color than that of the fresh blood. 
' The diluted blood gave with tincture of guaiacum a dirty, dark 
bluish-green color after long standing, and also a positive reaction 
