402 
BUIvI^ETlN OF THE BUREAU OE FISHERIES. 
find total destruction of cartilage and bone and marked evidences of infiltration of the 
bony and cartilaginous structures by individual cells and groups of cells. (Fig. 48 
and 49.) 
Infiltration of vessel walls. — Genuine infiltration of vessel walls will serve much the 
same purpose as infiltration of the capsule in mammals, as deposits of thyroid tissue 
within the media of the larger vessels has never been encountered. Figures 33 and 
50 show a section of the aortic wall stained with orcein, in which the elastic lamellae 
of the media are split up and spread out into the adjoining tumor mass as the result 
of the penetration between the elastic lamellae of the alveoli of an infiltrating tumor. 
The aortic wall at this point is reduced to about half the thickness of the uninfiltrated 
remainder of the circumference. We have here genuine infiltration of the media of the 
aorta. 
Infiltration of muscle. — Besides the growth of the alveoli of tumors between the 
muscle bundles (fig. 37), we frequently encounter infiltration of individual muscles cells 
by tumor cells. In these cases the sarcolemma sheath is broken through and we find 
the isolated cells of the tumor displacing the muscle fiber. (Fig. 51.) The tumor tissue 
in many instances has lost its alveolar structure, the cells being closely packed together 
without definite form. There are many instances of genuine infiltration by individuals 
or groups of cells in the muscle fibers. 
Infiltration of the skin. — This is usually best observed in the floor of the mouth. 
It has been suggested that the breaking through of tumor masses of the outer integu- 
ment was due largely to pressure, that the epidermis became greatly thinned and ulti- 
mately eroded. This is in many instances true where large masses of tumor protrude 
into the floor of the mouth or where protuberant growths extend downward or outward. 
In the floor of the mouth, however, we frequently find that the elastic structure of the" 
skin and the epithelial strata overlying it are punctured by small vegetations. Figures 
31 and 32 show such growths. Frequently growths penetrating the floor of the mouth 
will be found to have split up and destroyed the elastic structure of the epidermis without 
any appreciable thinning whatsoever, the entire thickness of the elastic structure sud- 
denly disintegrating without any evidence of stretching or thinning. (Fig. 46.) It 
is therefore evident that besides expansive growth, carcinoma of the thyroid in the Sal- 
monidae presents indisputable evidence of genuine infiltration, such as we encounter 
in malignant growths in other species. 
OTHER OBSERVATIONS. 
In 1905, T. Pick published a comprehensive article entitled “Carcinoma of the 
Thyroid in the Salmonidae, ” with 15 illustrations. It is by all means the most important 
publication on this subject dealing with the histology of these tumors. Pick’s material 
consisted of 10 brook trout obtained from a hatchery, we are led to believe, in the United 
States. He illustrates five of these fish, one of which exhibited a large infiltrating 
tumor involving the entire region below the floor of the mouth and the muscular struc- 
ture of the isthmus (Pick, 1905, fig. i). Figure 3 shows a small tumor at the branchial 
