454 REPORT OF THE HARVARD AFRICAN EXPEDITION 
cysts in the liver measured about 8 mm. in diameter. Eight other cysts were 
observed in the omentum of this animal. On section and microscopical ex- 
amination of a number of the cysts a single scolex measuring about 1.5 to 2.6 mm. 
in diameter was found in each cyst. Portions of the cysts and a number of 
the parasites themselves were preserved in alcohol. 
Histological study of the cysts and tissues about them show that the cyst 
is enclosed in a thin fibrous capsule in which there is marked infiltration with 
round cells and a few leucocytes. Among the infiltrating cells eosinophils are 
present in small numbers. Within this capsule is a layer or zone of delicate 

No. 391. — Photomicrograph of cyst wall of Taenia pisiformis 
vacuolated reticulated tissue which is not rich in nuclei. This layer of tissue 
is finally lined with an undulating, wavy membrane in which there are numerous 
closely placed filamentous papillae. This papilliform layer obviously con- 
stitutes the invaginating membrane. In a few places near or at the end of it 
may be seen the larval scolex. In other cysts where calcification has begun 
and perhaps where the death of the scolex has occurred, large numbers of len- 
ticular or elliptical calcified corpuscles may be observed in the tissue which pre- 
viously was evidently similar in structure to the delicate vacuolated areola 
tissue already referred to. The appearance of the undulating papilliform layer 
suggests that it may have the power of absorption of nourishment for the de- 
veloping scolex. 
Sandground, after clearing in lactophenol some of these cysts which were 
