180 CARNEGIE INSTITUTION OF WASHINGTON. 



organ, but in the absence of the necessary information the conclusions have 

 been unsatisfactory. Recent advances in biochemical technique now enable 

 us to make precise quantitative determinations of the various chemical com- 

 ponents in the nervous system, and it was the hope of the present writer to 

 obtain data which would assist in a comparative study of the metabolic 

 phenomena in the nervous system of vertebrates. 



The gray snapper was chosen for this investigation not only because these 

 fishes are abundant in subtropical seas, but also because they afford numerous 

 advantages for experimental purposes. The snapper may be kept in the 

 laboratory for a long period, and, in captivity as well as when free, takes almost 

 any kind of food, cooked or raw, animal or vegetable. The fish is well known 

 for sagaciousness and boldness and thus is suited for various kinds of experi- 

 mentation. Indeed the snapper has already been carefully studied by Reig- 

 hard (1908) as to its behavior. 



Altogether 44 snappers of medium size were used for the purpose of deter- 

 mining the various extractive nitrogenous substances in the brain. These 

 brains were divided into three samples, each giving approximately 10 grams of 

 moist brain-weight. The brains were ground finely and then preserved in 

 150 c.c. of a 2.5 per cent solution of trichloracetic acid in water. The filtrates 

 from this mixture have been brought back to the Wistar Institute for analysis. 

 I am of course unable to make any statement concerning the metabolic state 

 of the brain of this interesting fish until the analysis has been made, which 

 may take several months. 



In addition to obtaining the material mentioned, I have determined the 

 water-content of the brain from 64 snappers having various body-lengths 

 (90 to 450 mm.) . These brains also furnish material for the relative amount of 

 the lipoid and non-lipoid fractions — a relation to be contrasted with that found 

 in mammalian brains. This study also requires several months for the com- 

 pletion of the analysis, and at this moment I wish merely to express my great 

 satisfaction at being able to accumulate such valuable material. 



The Brain-weight in Relation to Body-length. 



The mathematical formula which enables one to estimate the probable 

 brain-weight in relation to body-length or body-weight has been determined 

 in the case of albino rats and it has proved highly useful when determining the 

 more or less minute changes in the brain under various experimental condi- 

 tions. 



With the hope that the gray snapper may in future prove to be a suitable 

 form for certain lines of experimental work, I have utilized all the brains 

 which have been used for the chemical investigation, together with some others, 

 for study of the growiih of the brain in weight with respect to body-length. 

 Altogether observations on 74 brains of the graj'- snapper have been recorded. 

 It is to be regretted, however, that the material, though amply sufficient for 

 the fish which are more than 200 mm. long, contains very few (only 3) measure- 

 ments for fish below 200 mm. Thus I am unable to make a study for the earlier 

 phases of the groAvth of brain in weight, but I feel safe in stating that in fish 

 over 200 mm. in length the relation between brain-weight and body-length is 

 linear and thus can be expressed by a veiy simple formula. I may say that 

 the fishes M'^hich are less than 200 mm. long are considered to be very small, 

 while those measuring more than 300 mm. are regarded as large. A most 

 careful search was made to find small snappers, but mthout success. It is 

 probable that the fry of the snapper may not live in the open sea or along 

 the beach, but may be hiding under the intricate roots of mangroves, trees 



