FAT-ABSORBING FUNCTION OF ALIMENTARY TRACT OF KING SALMON. 1 57 



in glycerin. Pure glycerin was used to make the mounts. Sealing with a mixture of 

 paraffin and beeswax around the cover glass was the final step in the mounting and 

 preservation of the sections. 



The more permanent sections of the tissues fixed as described were made by the 

 paraffin method, in which no special features in technique were introduced. 



The previous fixation in formalin was found to be decidedly advantageous in the 

 preparation of frozen sections. The brief time of immersion in the formalin does not 

 introduce a change in the character and distribution of the fats. On the other hand the 

 tissues are coagulated, hence firmer, and can be carried through the technique with a 

 much more satisfactory result. When the frozen sections were made directly from 

 fresh living tissues, then at the moment the frozen section was immersed in the alcohol 

 preliminary to the scarlet red staining, considerable contraction and sometimes tearing 

 took place. It was found that the distortion of the sections by this step was detrimental 

 to the securing of normal pictures of the structure and relations of the contained fat. 



SELECTION OF SPECIMENS. 



Two types of fish were used for the determination of the points detailed in this 

 report. First, salmon of various sizes and presumably of different ages collected from 

 the markets in the city of Monterey. The fish selected were those delivered directly 

 from the fishing boats, which had made their catch by trawling on the ocean fishing 

 banks in the vicinity. These fish came into the market with living tissues, a fact that 

 could easily be determined. The alimentary tracts were taken from the salmon at the 

 slaughtering tables of the fish-packing establishments of the Booth Packing Co." If 

 the tissues were proved to be alive in material chosen then histological samples were 

 selected and placed in fixative immediately, so that the question of prefixation changes 

 does not enter into consideration. 



The second class of material is that derived from young salmon collected from two 

 stations. The first collecting ground was that of the Brookdale hatchery maintained 

 in the town of that name on the San Lorenzo River in the Santa Cruz Mountains. Young 

 salmon were also obtained from the McCloud River in the Shasta ]\Iountains in northern 

 California. Both these groups of young salmon had never been in salt water. The 

 ages of the young salmon varied from one to two years, the latter being those obtained 

 at the ponds from Brookdale. 



NORMAL-FEEDING SALMON. 



The class of adult salmon mentioned above, which were secured at Monterey, were 

 in an active aggressive stage of ocean feeding. These salmon come into the markets 

 often with the stomach and intestinal tract gorged with food. The natural food is of a 

 varied class, but at Monterey consists mainly of three kinds: First, the squid; second, the 

 local species of herring; and, third, marine Crustacea, chiefly a rather large amphipod.* 

 The king salmon is a voracious feeder and his ability to capture a great variety of food 



1 For the courtesy extended by this company I am indebted to Mr. Frank E. Booth, the president. 



b In July, 19H. quite a number of sahnon were noted with large numbers of these Crustacea in their stomachs. One salmon 

 stomach in particular contained 4 or s (estimated) ounces of such food. It would have been interesting to have counted the 

 actual number of crustaceans present, but the content of the stomach was partly lost before the thought occurred to make such 

 an enumeration. 



19371°— vol 33—1.5 11 



