CARCINOMA OF THE THYROID IN SAEMONOID FISHES. 
499 
them the cockroaches, Periplaneta orientalis. These he identified as Filaria rhytipleurites 
of des Longchamps. After examining 6i rats from a locality in Copenhagen which 
was infested with Periplaneta americana, he found similar worms in the stomachs of 
40, of which 9 had well-developed tumors and 9 inflammatory reaction of the mucosa, 
which he held to be the beginning or precancerous stage of the disease. Furthermore, 
he reports that by feeding 57 laboratory rats with Periplaneta americana from the same 
locality he found the worms in the stomachs of 54, in 7 of which were definite tumors 
and 29 of which had the precancerous stage of the disease. Two of these tumors were 
found certainly to have metastases, probably three. The metastases did not contain 
the nematodes, and furthermore, Fibiger states that there is no direct relation between 
the intensity or amount of proliferation and the location of the worms in the gastric 
mucosa. 
The life history of these worms is as follows: They live in the squamous epithelium 
of the esophagus and stomach of the rat. In rare cases they are found in the epithelium 
of the tongue and the mouth cavity. Here they reach the reproductive stage and eject 
eggs which, with the desquamated epithelium, are carried out with the excreta. In the 
excreta they are taken up by the cockroach Periplaneta onentalis, and in these insects 
the eggs develop into free embryos, wander into the striated musculature of the pro- 
thorax and the extremities. Here they remain for about six weeks or a longer time as 
trichina-like spirally coiled larvae. If the cockroaches are consr.med by the rats the 
larvae are freed from their capsules and wander into the squamous epithelium of the 
rat’s stomach, occasionally into the esophagus or the epithelium of the mouth or tongue. 
Here after two months the female begins to deposit eggs. The measurements of these 
worms in the fully developed stage are, for the male, one-half to i centimeter long, 
diameter, o.i to 0.16 millimeter; females, 4 to 5 centimeters long; diameter, 0.2 to 
0.25 millimeter. The eggs are oval, clear, with double contour membrane, at the 
poles slightly thicker than at the circumference. The eggs measure 0.06 by 0.04 
millimeter. They contain a rolled-up embryo with annular divisions of the cuticle. 
They have been identified as belonging to the genus Spiroptera. The male has a large 
bursa, with two spicules of different lengths and four preanal, as well as four postanal 
papillae, on each side, these characteristics serving to distinguish them from the Spiroptera 
obtusa, as well as from the Filaria rhytipleurites of Galeb. It is therefore a new 
nematode. 
In the sections of the hyperplastic thyroids in our second series of experimental 
dogs, we were interested to find in the capsule and in the substance of the thyroid small 
tubercles measuring usually 0.3 by 0.35 millimeter, of strikingly uniform appearance. 
At the periphery of these tubercles is a fibrous connective tissue capsule of thin and 
flattened cells. Within the outer layer of flattened fibrous connective tissue a more 
cellular structure composes the body of the tubercle. These are large fibroblasts of 
spindle form with oval, vesicular nuclei. They have a general arrangement, as if per- 
pendicular to the circumference. The center of the tubercle is composed of intercellular 
substance with usually a zone of leucocytes, and by aid of serial sections, usually in the 
center of these tubercles, one encounters a cross or oblique section of a small nematode 
