31 
of both varieties. The cells take up the organism, the polymorpho- 
nuclear forms degenerate; the mononuclear cells are, however, capa- 
ble of further development, and, probably with the assistance of 
connective tissue cells, form the epithelioid and giant cells. Inclosed 
within their^cell prison the bacilli undergo a gradual disintegration, 
setting free a poison which may produce partial death of a ceh, or, 
if in sufficient quantity, may produce the death of many cells. There 
is not the same activity m the leucocytes, nor the same vacuolation 
of the protoplasm and development of pseudopodia in the mono- 
nuclear forms. The epithelioid cells have not the same size or the 
same branched appearance, the giant cells are more rounded and 
smooth. The whole process gives one the impression of less activity. 
In the later stages the difference is more marked. There is not the 
same wide distribution and extension of the process, nor is there the 
same constant addition of new phagocytes at the margin which will 
become epithelioid cells and help to swell the giant cell. There is, 
however, in these later stages the same impression of a partial cell 
necrosis. The bacilli disappear, but the cells persist and show the 
peculiar hyalme appearance. Further, there is the same polymorpho- 
nuclear leucocytosis in the last stage of pseudo-tubercle that we have 
seen m true tubercle.’’ 
In my own experiments, in order to avoid the confusion resulting 
from the effects produced by dead tubercle bacilli, doubtfid lesions 
were carried over into another animal. These “secondary” guinea 
pigs appear in Tables Xos. 1 to 9. The method used was as follows: 
The lesions, and sometunes the organs, were ground up in a mortar 
with salt solution, strained through gauze, and the extract thus 
obtained injected mto the peritoneal cavity of a young normal guinea 
pig. Only two of these secondary guinea pigs developed generalized 
tuberculosis. The others remained well, gained weight, failed to 
respond to tuberculm, and gave no evidence of an active tubercu- 
losis at necropsy. Some of these secondary animals had small 
tuberclelike masses in the omentum, due to absorption of the prod- 
ucts introduced into the peritoneal cavity. 
Almost all the animals were tested with tuberculin m the hope 
that this test might distmguish between the lesions of live and of dead 
tubercle bacilli. This, however, was found not to be the case, for when 
the eight animals with lesions caused by tubercle bacilli known to 
be dead, were injected with 2 c. c. of tuberculm (O. T.) (see Table No. 
10), three of them died. The series of guinea pigs in this table is 
instructive further in that it illustrates that dead tubercle bacilli in 
milk, when injected into the peritoneal cavity, may produce very 
extensive tubercular lesions with coagulation necroses (caseation), etc. 
31685— Bull. 42—08 3 
