PSEUDO ACTINOMYCES OF THE UDDER OF THE COW 373 
Inoculation Experiments 
Three guinea pigs were inoculated, December 2nd, 1901, subcutaneously in the 
groin with an emulsion made by crushing the contents ot several of the nodules in 
sterilised water ; about 1 c.c. of the emulsion was inoculated into each guinea pig. 
At the end of one week the animals were examined, in two no reaction could be felt 
at the seat of inoculation, but in the third there was a slight swelling. The animals 
were kept under observation till December 2 1 St. Nos. 1 and 2 still showed no trace 
of reaction, and in No. 3 the hard swelling had slightly decreased in size ; it was, 
therefore, determined to kill and examine the guinea pig which showed the reaction. 
The autopsy revealed a small circumscribed local swelling at the seat of inoculation, 
and with this exception, all the organs appeared quite normal. A coverslip prepara- 
tion was made from the swelling and stained and examined, but no hyphae or bacteria 
were found. The tissue was then hardened and stained, as in the case of the original 
nodules. 
Careful microscopic examination of these sections showed numerous fragments 
of club-like bodies, and of bits of the ray-like nodules scattered amongst leucocytes 
and lymphoid cells. There was not a trace, however, or any hyphal structure, or 
anything approaching the tufts ot the true ray fungus. These experiments show that 
the fungus-like masses in the nodules, if they really were of the nature of a fungus-like 
actinomyces, were not alive at the time of inoculation. 
Microscopical Structure of the Tissue. 
The pieces ot the mammary gland, containing the circumscribed nodules, were 
hardened in four per cent, solution of formaline and cut in paraffin. 
The sections were stained by the following methods : — 
j. Haematoxylin. 
2. Methylene Blue. 
3. Gram's method. 
4. Fuchsin and Methylene Blue. 
5. Phenol-Thionin. 
Fig. 1 is a section under the low power (ij" obj.) which shows about one- 
third of a nodule embedded in the interstitial tissue of the udder, and surrounded 
by gland tissue. The small violet mass in the nodule represents the mulberry-like 
mass, stained by Gram's method. Outside the nodule the mammary tissue appears 
normal, and is that of the actively secreting gland. Under the high power the nodule 
is seen to be made up of numerous small round cells, consisting of lymphoid cells, 
connective tissue cells, and leucocytes, there are no giant cells. The periphery of 
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