278 ANNUAL OF SCIENTIFIC DISCO\'ERT. 



ters of the food, the much lavg^er amount of fat prodticpfl, both in 

 rehition to a given weight of aninuil within a given time and to 

 the amount of food consumed, tlie much less proportion of the 

 solid matter of the food that passed off in the solid and liquid ex- 

 cretions, and liiKilly tlie larger proportion of fat in the increase, 

 results ol)tained with pigs must he much more eonelusive than 

 those with either cows, oxen, or sheep. Numerous tables wvm 

 exhibited, showing the results which had been obtained bj' tiie 

 authors in experiments with l)igs, from which the following con- 

 clusions were drawn: 1. That certainly a large proportion of the 

 fat of the Herbivora, fattened for human food, must be derived 

 from other substances than fat in the food. 2. That when fed on 

 the ujost apjiropriate fattening food, nnich of the stored up fat 

 must be produced from the carl)0-hydrates. 3. That the nitro- 

 genous constituents may also s(!rve as a source of fat, more espe- 

 ciall}' in defect of a liberal supjily of the non-nitrogenous ones. , 



VELOCITY OF NERVOUS IMPRESSIONS. 



!^^r. "W. F. Barrett communicates to the " Intellectual Observer," 

 for June, l.S(3(], a j^aper " On the Velocity of Nervous Impressions," 

 from which tiie following are exti'acts : — 



"What, then, is the result of the investigations of Ilelmholtz on 

 the velocity of the nerve force? It is one wliieh, at first sight, is 

 most astonishing; for the rate of ))ropagation, compared with 

 other forces, is extremely slow. The velocity of liglit is altout 

 190,000 miles a second, and of electricity even more ; but the ve- 

 locity of the nerve force is only ninety feet a second, one-twentieth 

 of the velocity of a camion ball, about one-thirteenth of the veloc- 

 ity of sound in air, and about equal to the speed of an express 

 train. No sensible difference was found between the velocity in 

 the nei'ves of a man, and in those of a frog and other animals. In 

 a creature so long as the whale, tiie rate of nervous transmission 

 becomes very perceptible when the extremities have to be moved. 

 The fact of a harpoon having been thrust into the tail of a good- 

 sized whale would not be announced in the brain of the creature 

 till a second after it had entered ; and, as it would take a little 

 more than another second before the command to move its tail 

 would i-each the appropriate muscles, a boat's crew might be far 

 away before the animal they had pierced began to lash the sea. 

 Tlie nervous force travels more slowly when the nerves are sub- 

 mitted to a low temperature than when they are influenced by a 

 high one. Besides the time required for the transmission of a 

 stimulus through the nerves, the mind takes a certain period to 

 form a conception, and then to prompt the limbs to act accordingly. 

 This time, measured by a similar method, has been found to be 

 about one-tenth of a second. The passage of a rifle-bullet thi-ough 

 the brain would not occupy more than one-thousandth of a second ; 

 a stroke of lightning would pass through the body in much less 

 time ; and thus a person killed by either of these means would die 

 without consciousness having time to be produced. The placid 

 aspect of those who hive thus died goes to prove that no pain was 

 felt prior to the insensibility which followed the act. 



