ONCHOCERCIASIS 247 
Histological examination of the different tumors collected in various localities 
in Africa, show that they are all fibromata. In the center, sections of the adult 
parasites are commonly found (No. 184) usually imbedded in the connective tissue 
stroma. Immediately about the parasites there is often some evidence of irri- 
tation caused by the parasite itself. A few polymorphonuclear leucocytes are 
scattered about with small round cells, occasionally plasma cells, and eosino- 
phils. Outside of these areas the tumor is composed largely of fibrous connective 
tissue. Here the fibroblasts are few in number and the fibroglia fibrils are not 
abundant. The tumor is composed particularly of collagen fibers forming wavy 
bundles (No. 186). In none of the tumors do the cells show marked evidence of 
mitotic division, nor are numerous giant cells present, so there is no evidence 
that the neoplasms are formed very rapidly. 
From an examination of Photomicrograph No. 188 it may be seen that some- 
times there is no evidence of inflammatory change about the sections of the 
adult parasites which are surrounded on all sides by wide bands of connective 
tissue in which collagen fibers predominate. In other instances there is a clear 
space about the section of the parasite (No. 189) which is partially surrounded 
by a thin layer of coagulated lymph in which fibrin and small round cells, and 
polymorphonuclear leucocytes as well as a few plasma cells, are visible. The 
surrounding connective tissue in such sections (taken apparently from tumors 
or areas of more rapid growth) is much richer in nuclei. These nuclei are more 
often round or oval, but are sometimes spindle-shaped. In some areas the ap- 
pearance is somewhat suggestive of the condition observed in fibrosarcomata. 
Giant cells are present m some areas but are not abundant. In certain portions 
of the tumor the eosinophils are markedly increased, a condition, however, not 
usually found in the immediate vicinity of the sections of the adult parasites. 
Sometimes small clumps of eosinophils are observed. The microfilariae (No. 
190) are found in large numbers in many but not in all parts of the tumors. 
In many areas in which they are prevalent, the round or oval nuclei of the fibro- 
blasts predominate in the surrounding tissue. Frequently there is a clear space 
or opening in the tissue about the organisms. Rarely are there accumulations 
of round cells or polymorphonuclear leucocytes about them, but such reaction 
is present in a few areas. 
There seems to be no doubt but that the parasite is the inciting factor in the 
formation of the neoplasms. 
Other Pathological Effects Caused by Onchocerca. A marked difference is noted 
with reference to the larvae of Onchocerca volvulus and the microfilariae of Wwucher- 
erta bancrofti and Acanthocheilonema perstans, in that the larval forms of On- 
chocerca are rarely present under normal conditions in the circulating blood. 
When they are encountered among blood cells their presence usually may be 
explained by the fact that lymph spaces have been punctured in securing the 
specimens. Sharp‘! who examined the blood of 2000 cases, examined by thick 
film method, found that the embryos occurred in eight per cent. The larval 
forms of Onchocerca, however, as we have illustrated, are usually found in con- 
1 Sharp: Proc. Royal Soc. Med. (1927), XX, 41. 
