356 ELDON W. SANFORD 
sorbing food, the various functions of the gizzard, the details 
and significance of digestive processes in the stomach and coeca, 
and the explanation of the presence of certain substances and 
leucocytes in the tracheal tubes. 
MATERIAL AND METHODS 
The material first used consisted in the species of cockroach 
previously used by most earlier investigators in the field of fat 
digestion in insects, namely, Blatta orientalis Linnaeus (Peri- 
planeta orientalis), the common black cockroach, and Blatella 
(Philodromia) germanica, the croton bug. The latter species 
was found rather small for convenient dissection and observa- 
tion. Later on I used Periplaneta americana, the American 
cockroach, almost exclusively. In this species, which is very 
hardy and much larger, it seemed hopeful that some processes 
which had been obscure or disputed in the smaller species might 
be seen more plainly, and indeed this proved to be the case. 
One especially fortunate fact was discovered, namely, that the 
body cavity in the abdominal region could be entered in the 
living animal by turning back a flap of the body wall. After the 
flap was replaced, the animal experienced no serious incon- 
venience. It was found possible thus to make ligations of the 
alimentary canal just after food was taken, thus isolating certain 
digestive organs from connection with others. This eliminated 
the uncertainty of previous work as to the flowing of digestive 
juices from one part to another. The digestion which occurred 
in a part tightly ligated from other parts was considered to be 
surely produced by digestive fluids and enzymes secreted in 
that part. 
Another fortunate feature about Periplaneta americana is its 
tolerance of sunlight. Unlike Blatta orientalis, which is very 
sensitive to light and avoids it whenever possible, my animals 
walked around contentedly even in bright light and took food 
normally. 
The tissues were usually fixed in Flemming’s strong solution, 
which contains osmic acid and stains fats black by an oxidative 
process. This fixing fluid is especially effective in work with 
