CARCINOMA OF THE THYROID IN SALMONOID FISHES. 499 



them the cockroaches, Periplaneta orientalis. These he identified as Filaria rhytipleurites 

 of des Longchamps. After examining 61 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 orientalis, 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 consumed 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 



