40 SUMMARY OF CURRENT RESEARCHES RELATING TO 



smaller. The sensory ridges are located on crests or portions of the 

 canal approaching the surface. The lumen of the canal here is always 

 larger than just anterior or posterior to the ridge. The longest ridges 

 are in the anterior region. There is a gradual diminution in length in 

 a posterior direction until just before the tail is reached. Upon the 

 tail itself a slight increase in length occurs. No branchlet, except 

 on the caudal fin, where there seems to be great irregularity, is given 

 off without a sensory ridge at its posterior end. Ridges may or may 

 not occur between the branchlets. Though there is a slight grouping, 

 branchlets are given off throughout the entire length of the lateral 

 canal. J. A. T. 



Investigations on the Spiroptera Cancer, III.-VI. — Johannes 

 FiBiGER {Det. Kgl. Danshe Videnskahernes SelsJcab. Biologiske Meddelelser^ 

 1918-19, 1, 9, 10, 11, 14). Following on his previous observations on 

 the development of carcinoma in 12 black and white laboratory rats 

 infected with a round worm, Spiroptera neoplastica, Johannes Fibiger 

 records further similar experiments on 214 black and white laboratory 

 rats. Of these, 102 rats survived more than 45 days, of whom 54 

 (53 p.c.) developed carcinoma of the fundus of the stomach. His ability 

 to produce carcinoma at will is a big step forward in the investigation 

 of the origin of tumour cells from normal tissue, as transplantion experi- 

 ments only permit of the study of the continued propagation of fully- 

 developed spontaneous tumours. The experiments consisted of feeding 

 the animals with the muscles of cockroaches {Feriplaneta americana and 

 P. orientalis) infected with the larvae of Spiroptera neoplastica. The 

 cockroaches were fed on the excrement of rats containing the eggs of 

 the parasite. The nematode lives attached to the pavement epithelium 

 of the mouth and fundus of the stomach. 



Out of 116 rats, in 107 the fundus was examined in serial section. 

 This was necessary in that the growth may be too slight to be seen 

 microscopically, as rats surviving IJ to 3 months after infection showed 

 carcinomata of only 1 mm. in extent, but in those living up to 6 months 

 the growth reached 2*5 to 5 mm. The earliest development of carci- 

 noma was 45 to 50 days after infection with the larvag. 



Carcinoma was only diagnosed on : — 1. The heterotopical down- 

 growth of epithelial cells belonging not only to the normal type of the 

 basal epithelial layers, but mixed up with atypical and keratinized cells 

 partly arranged as spherical masses and horny globes. 2. Infiltration of 

 these cells into the deeper layers splitting up invasively the connective 

 tissue of the mucosa and muscle cells of muscularis mucosae, forming 

 islets and spurs in the latter or penetrating through this layer into the 

 submucosa. Metastases occurred in 8 cases, and contained no worms or 

 ova. Also carcinomatous growth continued after all the Spiroptera had 

 disappeared from the stomach. Whereas previously, as he points out, 

 there have been only 10 (about) recorded cases of cancer of the tongue 

 in domestic animals and none in rats, he has succeeded in the production 

 in rats of 6 cases, 5 by Spiroptera infection and 1 by feeding with oats. 

 One hundred and fifteen tongues were examined in serial section (at 

 10 /x every 10th to 6th or more of which were examined), comprising 



