( 1074 ) 
of the germs. As endo-enzymes may be considered as constituents 
of the proteplasm, it is not surprising that the reactions with such 
preparations, containing only dead material, are feeble, for the enzyme 
itself is for the greater part annihilated. Hence, in my opinion, 
endo-enzymes are best studied when still within the living cells 
themselves and by considering them as an essential part of the 
living protoplasm. Taken in this sense tyrosinase may be called a 
“respiration enzyme’, and it is remarkable that as a product of 
respiration, beside the carbonic acid, ammonia is formed, instead 
of water as in the ordinary respiration. 
In sewage water only a small number of tyrosine bacteria are 
found per cM*. This number may be a little increased by leaving 
the sewage water for some time at room temperature, then making 
on plates streaks of the microbes accumulated in the layer at 
the surface. This microbe layer, very rich in infusoria and flagel- 
lates, produces, in particular as it seems in late summer, many 
more tyrosine bacteria than the sewage water itself. Nevertheless, 
as said above, it has not been possible to find a really” good 
accumulation method of these tyrosine bacteria, although many trials 
have been made. 
The black pigment can be prepared in great quantities by cultivating 
the pure microbes at 30° C. in large ERLENMEYER flasks of the said 
feebly alkaline solution of natriumtyrosinate with the required anorganic 
salts. The conversion is relatively slow, so that it is complete only 
after some weeks, but then a liquid is obtained which may be used 
as ink. Traces of ferrisalts favour somewhat the formation of 
melanine. 
The tyrosine bacteria belong to the genus J/icrospira created by 
Mievra. They are very small polar-monociliate, curved rodlets, some- 
what varying in thickness, mostly thinner than the cholera vibrios, 
which for the rest they resemble very much. Like these they quickly 
liquefy broth gelatin and form on broth agar white, vigorously 
growing soft masses. Sometimes they are vnited in long chains; the 
longest individuals show distinct curves and remind of spirilli. If 
tyrosine is present in the nutrient medium, many individuals take 
partly a black colour, swelling up very much and sometimes 
becoming quite spherical, but the cilia do not become visible. They 
produce indol, but do not give the nitrosoindol reaction. They grow 
well in peptone solutions. 
The fresh-water form colours broth agar without tyrosine not 
or only very late, but if tyrosine is added the brothagar grows 
rapidly black. The black-colouring begins still earlier on the before 
