PROGRESS OF VETERINARY SCIENCE AND ART. 151 
coloration of the whole constituents of the milk, which now 
emits an acid odour sometimes approaching to fetidity. Either 
butter or cheese made of the cream soon becomes mouldy, 
with the development of parasitic animals and vegetables. 
Delafond, from whom I am largely borrowing in these re- 
marks, says that this condition of milk is only seen in the 
spring, summer, and autumn, never in winter. The cows 
are in health, the mammae likewise, the milk then changes in 
consequence of some cause extraneous to the system. 
Hermsbstadt first thought it was due to cows feeding on 
plants containing indigo. Parmentier and Deyeux, in 1 8 1 5, 
Braconnot in 1836, and Bailleul in 1843, emitted the opinion 
that it was a cryptogamic plant coloured the secretion, and 
Braconnot thought it was the bisms carula . Professor Fuchs 
of the Veterinary School of Carlsruhe, at last discovered 
that an infusorial animalcule, a vibrio, which he called vibrio 
cyanogenus , produced the blue colour, and the number of 
these animals in a single speck is incalculable. Fuchs has 
approximatively reckoned that 40,000 would be required to 
cover a square line. Placing a drop of the coloured milk 
with some that is normal, this speedily experiences a similar 
change. 
Here it is I have to quote Dr. Quidde’s article treating on 
the causes of blue milk. He says, that from observations 
carried out in various localities, he is persuaded the milk of 
cows readily acquires the blue colour when the cows have 
been fed on bad food. Marred and mouldy clover, musty 
hay, spoiled fermenting grains all leading to a perverted con- 
dition of the blood, hence of its secretions ; the milk acquiring 
a special tendency to ferment, and constituting a favorable 
site for the deposition of germs and development of infusoria. 
This is especially seen in those dairies in which there is little 
ventilation and a peculiar tendency to the accumulation of 
germs. Experiments have, moreover, proved that pure milk 
from healthily nourished cows, even if placed under the same 
conditions, that is to say, in ill-ventilated dairies, as that 
becoming blue, does not become discoloured. Quidde, there- 
fore, concludes that badly feeding the cows, and the milk being 
allowed to stand in foul chambers, or kept in dirty pans, are 
the two reasons accounting for the development of the vibrio 
cyanogenus. 
There is yellow milk as well as blue, and this has been attri- 
buted also to cows feeding on vegetables, containing a yellow 
colouring matter. Fuchs, however, has discovered in this 
form, also, that a yellow vibrio is developed which he calls 
the vibrio xantogenus. 
