CARCINOMA OF THE THYROID IN SARMONOID FISHES. 
447 
that for recruits who have reached the age for military service for the district, 9.22 
per cent. From this it would appear that there is a steady increase of goiter in school 
children up to the age of puberty, with a marked decrease between that age and 20. 
Our tables show that for brook trout yearling fish the maximum is 28 per cent, 
.or 2-year-olds 65 per cent, and for fish older than 2 years 91 per cent. It may be 
stated for brook trout in captivity that a large proportion of them at least have acquired 
their reproductive faculties in the second year and that their full reproductive faculties 
are certainly acquired by the third season. It thus appears from our figures that fish 
exhibit a very high, probably the highest, incidence in the period from 2 to 5 years, 
which in the life of a fish carries it well beyond the comparable period in human beings. 
We have frequently met with instances of actively growing tumors in the oldest fish 
under observation and the large tumors in old fish have never presented an appearance 
comparable to colloid goiter. So far as this comparison is admissible it would indicate 
that the process in the fish in its age incidence is more in accord with McCarrison’s 
observations than the Bavarian statistics just quoted. Both McCarrison’s statistics 
for man in Chitral and Gilgit and our own for fish reach well into the period of increasing 
incidence of neoplasms in mammals. 
HEMOGLOBIN ESTIMATIONS. 
In the autumn of 1902, before thyroid carcinoma in fishes had attracted attention 
in this country, one of us observed, incidental to work upon bacterial infection in trout,, 
an anemic condition among a certain lot of brook trout at a State hatchery at Paris, 
Mich. These fish were i^ years old and were part of a lot of several hundred which 
had been sorted and segregated from the general hatchery stock on account of their 
undersized and stunted condition. Except for their small size this lot was in fair 
condition and most of them would have spawned for the first time some weeks subse- 
quent to these observations. Of this selected lot the percentage having tumors was 
not determined but there were more normal healthy fish than those bearing tumors. 
Even the tumor fish with anemia showed no particular emaciation or falling off in 
condition. 
Nine apparently healthy fish without tumors were taken at random from this lot 
and hemoglobin readings obtained. Nineteen tumor fish from the same lot then had 
their hemoglobin estimated in the same way. The range of the former was from 30 to 
43, of the latter from almost nothing to 47, the averages being 37.5 and 21 .6, respectively. 
The readings were made with a Dare hemoglobinometer; those recorded as 8 are arbi- 
trarily overstated, the samples scarcely showing red and registering much below the 
lowest scale reading. The fish showing the highest reading (47) had only a very small 
tumor, in the jugular pit. The largest fish of the series (first of the table) showed one 
of the lowest readings, and had marked blood changes. The tumors were not measured 
or accurately compared, but the larger usually gave the lowest readings. A marked 
poikilocytosis accompanied a low blood count for red cells. The normal red cells 
numbered 256,000 per cubic millimeter, or 416,000 including the atypical reds of extra- 
ordinarily small size. The red cells of normal brook trout blood number about i ,000,000 
per cubic millimeter. 
