ii2 Shiro Tashiro 



Non-Medullated Nerve Fibre. (The nerve of the spider crab, 

 and apparatus 2 for the qualitative, and apparatus i, for the quanti- 

 tative, estimations were used.) When I place the nerve of a spider 

 crab in the right chamber and no nerve in the left, and watch for the 

 deposit of barium carbonate, the drop on the right will soon be coated 

 with the white precipitate, but no precipitate whatever is visible with 

 a lens in the left. ,C0 2 is thus shown to be produced by this resting 

 nerve. Now, by interchanging the nerve from the right to the left, 

 no nerve being in the right, we can convince ourselves of the correct- 

 ness of this conclusion, by eliminating any technical error which might 

 produce the different results in different chambers. The rate at which 

 the precipitate appears and the quantity of the precipitate, depends 

 on the size of the nerve. In fact, C0 2 production from the resting 

 nerve of the spider crab is found to be proportional to its weight, 

 other things being equal, and is constant: For 10 milligrams per ten 

 minutes it gives 6.7 X -io- 7 grams at 15 i6c. 



The quantitative determination of this amount is made in the 

 following manner : 



The claws of the crab are carefully removed, and, by gently 

 cracking them, the long fibre of the nerve trunk is easily isolated. 

 After removing the last drops of the water by a filter paper, the nerve, 

 with the aid of glass chop sticks, is carefully placed on the glass plate, 20 

 and quickly weighed. The glass plate with the nerve is now hung 

 on the platinum hooks in the respiratory chamber A, and then the 

 .chamber sealed with mercury. The analytic chamber is now filled 

 with mercury in the manner described elsewhere, 21 and then the 

 apparatus is washed by C02 free air as usual. The time when the 

 barium hydroxide is introduced to the cup in chamber B is recorded, 

 and the stop-cock between the two chambers is closed. When at 

 the end of ten minutes the drop at cut F is perfectly clear, having not 

 a single granule of the precipitate visible to a lens, thus insuring that 

 the air is absolutely free from CO 2 then a known portion of the gas 

 from the respiratory chamber is introduced into the chamber below 

 in which the clear drop of barium hydroxide has been exposed, and it 

 is determined whether or not the amount of the gas taken contains 



20 The weight of this plate is known so that the weight of the nerve can be 

 determined very quickly. See p. 120. 



21 See pp. 139. 



