208 R. KOCH. 
case only by means of the organs of digestion, and in accordance with this the first 
appearances of the disease must first show themselves here. But now primary tuber¬ 
culosis of the intestines is not at all freduent in proportion to primary lung-tubercu¬ 
losis—indeed, a decidedly rare affection. From this it is to be concluded, that the 
infection in question does not often occur from eating the flesh of tuberculous 
animals. Probably it would occur frequently if the visibly diseased parts of the 
flesh were not put aside, as is usually the case, and if, as is almost invariably the 
case, the meat were not eaten cooked. Also especially it must be considered that 
the tuberculosis eatable animals, especially the perlsucht of cattle, remains more or 
less localized, so that after all only the use of the tuberculously altered lungs, 
glands, etc., would be dangerous. That, nevertheless, the infection from the in¬ 
testinal canal is indeed possible, is proved by the frequent cases of secondary in¬ 
testinal tuberculosis of consumptives, which must be attributed to the swallowing 
of their own sputa. It is, to be sure, strange that, although it is to be supposed, 
that every consumptive swallows more or less of the tuberculous bacilli-bearing 
secretion from his lungs, nevertheless intestinal abscesses are not to be found in 
all. I explain this in the following manner : In the first place, the intestines ap¬ 
pear to offer a still more unfavorable point of attack for the slowly growing tuber¬ 
culous bacilli than the lungs. But further, the feeding-attempts with anthrax 
bacilli and their spores, have taught that anthrax bacilli, which contain no 
spores, are destroyed in the stomach, while the spores of these bacilli are 
able to pass through the stomach unharmed. On that account only spore¬ 
bearing substances can cause infection from the intestinal canal. The tuberculous 
bacilli will conduct themselves most probably in this regard, like the anthrax- 
bacilli, and only in case they are provided with spores will cause tuberculosis of 
the intestines, provided they do not go through the intestinal canal too quickly to 
render their germinating and establishing themselves at any point of the mucous 
membrane of the intestines possible. Just the same holds, of course, for the danger 
of an infection from tuberculous meat, and this circumstance may explain the 
relatively rare infection from the use of such meat. 
The same conditions hold for infection from the milk of cows suffering from 
perlsucht. Before all things, if infection is to take place it is necessary that the 
milk contain tuberculous bacilli. But this appears only to be the case when the 
milk-glands themselves are tuberculously diseased. But since perlsucht-knots do 
not often occur in the udder, the milk of perlsucht cows will often possess no in¬ 
fectious properties. This explains immediately the contradictions in the state¬ 
ments of the various authors, who have made feeding attempts with milk from 
cows suffering from perlsucht. The one set maintain that they have gained posi¬ 
tive results, and their statements are of such a sort that it is impossible to doubt 
the correctness of their observations. The others, on the contrary, could obtain 
no infection in the animals experimented with. This result is also correct. The 
positive results were then obtained from milk which accidentally contained tuber¬ 
culous bacilli, the negative wiffi milk which was free from bacilli. 
If infection from tuberculous domestic animals in general does not appear 
to be frequent, it must by no means be under-rated. Perlsucht of cattle and the 
caseous changes in the lymph-glands of pigs are of so frequent occurrence that 
they deserve close attention. If, now, we follow the tuberculous bacilli which 
