PHYSIOLOGY. 



721 



with careful attention to avoiding the sources of 

 error to which previous experiments were liable. 

 The conclusions are adduced that lesions of the 

 white substance are incompetent to produce a 

 rise of temperature unless they touch the gray 

 matter of the central ganglia; that lesions of 

 the corpus striatum produce usually a consider- 

 able rise ; that when the optic thalamus is in- 

 jured, the rise attains its highest point in six or 

 seven hours and has an average duration of forty 

 hours; and, on the whole, that the corpus 

 striatum and the optic thalamus have, in rabbits 

 at least, the power of modifying the temperature 

 -of the body, and that the surrounding white 

 matter has no such function. A similar result 

 has been observed in man in cases of patients 

 who were under the author's care. 



The questions have been investigated by 

 Humphry D. Rolleston whether there is any 

 evolution of heat during the passage of a nerv- 

 ous impulse, and as to the production of heat 

 in a nerve during the process of dying. The 

 first question is answered in the negative, no 

 evidence having been produced in the experi- 

 ments of any heat being evolved from the nerve 

 trunk; and the second question affirmatively, 

 the dying nerve having evolved enough heat to 

 raise the temperature of the thermometer in 

 contact with it | C. The evolution of heat 

 roughly corresponds with the intensity of the 

 natural nerve current, but this is not constant 

 absolutely. There is some evidence to show that 

 nerves die at different rates. 



In the experiments of Dr. Joseph on the in- 

 fluence of the nerves on the skin, a piece of the 

 second cervical nerve was excised from the 

 ganglion. A few days afterward, the author ob- 

 served behind the ear of the side operated upon 

 a circumscribed spot from which the hair had 

 fallen out, but which indicated no other change. 

 By microscopic examination the hair papilla? and 

 the hair roots were found to be absent from the 

 hairless spot, while the other constituents of the 

 skin remained as they were. The author regarded 

 this result as evidence of the existence of trophic 

 nerves. 



The physiology of fatigue has been the sub- 

 ject of elaborate researches, the results of which 

 are still indeterminate. In regard to the points 

 of the nervous system first affected, Dr. G. V. 

 Poore, in his papers on " Writer's Cramp " and 

 allied affections, adduces facts that tend to sup- 

 port the hypothesis that they are situated in the 

 peripheral apparatus. The experimental evi- 

 dence adduced by Dr. Augustus Waller is con- 

 firmatory of this view. The pathological mani- 

 festations are also not sufficiently understood. 

 Prof. Angelo Mosso says that fatigue carried be- 

 yond the moderate stage, at which it is bene- 

 ficial, subjects the blood to a decomposing pro- 

 cess through the infiltration into it of substances 

 which act as poisons substances which, when 

 injected into the circulation of healthy animals, 

 induce malaise and all the signs of excessive ex- 

 haustion. That the chief cause of fatigue is the 

 production of certain substances and their action 

 on the tissues is not a self-evident proposition, 

 because it seems to be clear that any tissue ex- 

 cited unduly in a given space of time must be- 

 come exhausted. And it is equally possible that 

 fatigue as a sensation may be caused by the nega- 

 VOL. xxx. 46 A 



tive condition of diminished reconstruction as 

 well as by the positive one of actual irritation by 

 the products of metabolism. The facts at ; 

 ent ascertained seem to prove that the negati\.- 

 and the positive states are both operative in the 

 causation of fatigue. 



A study of electrical currents in the skin from 

 mental excitation has been made by Ilerr Tiuvh- 

 enoff. Unpolarizable clay electrodes, connected 

 with a delicate galvanometer, were applied to 

 various parts, and after compensation of any 

 currents that occurred during rest, the effects of 

 mental stimulation were noted. Light tickling 

 with a brush, hot water, sound, light, taste, and 

 smell stimuli caused, after a brief period of 

 latency, a gradually increasing deflection ; cold, 

 or the pain from a needle prick, the same effect 

 in a less degree. If the eyes have been closed 

 for some time, the mere opening of them causes 

 a considerable deflection from the skin of the 

 hand. Different colors here acted unequally. 

 The currents also arise when the sensations are 

 merely imagined. Mental effort produces cur- 

 rents varying with its amount. Under tense ex- 

 pectation the oscillations are irregular. When 

 the electrodes are on the hand or arm, a volun- 

 tary movement gives a strong current. In all the 

 experiments it appeared that, with equal nerve 

 excitation, the strength of the skin currents de- 

 pended on the degree to which the part of the 

 skin bearing the electrodes was furnished with 

 sweat glands. 



It appears from the researches of Dr. Gold- 

 scheider, of Berlin, that the sensitiveness of the 

 articular surfaces of joints is dependent not so 

 much upon the irritability of the surfaces of the 

 joints as on that of the epiphyses. The great- 

 est effect was produced by direct stimulation of 

 the marrow of the respective bones, while stimu- 

 lation of the compact bone substance showed 

 that this was insensitive. 



Circulation. As the result of his studies on 

 the blood corpuscles, Dr. C. S. Minot reports the 

 conclusion that they are derived from cells in the 

 interior of the primitive blood vessels, these cells 

 resulting from a multiplication of the cells com- 

 posing the vessel walls. The corpuscle thus formed 

 gains, in its mature stage, by an increase of its 

 protoplasm. In some animals the nucleus syn- 

 chronously diminishes. These are the red 

 corpuscles. The white corpuscles are formed 

 in the tissues by a change from certain tis- 

 sue cells derived from the middle embry- 

 onic layer. These appear in the blood at the 

 time when the red cells are about half-way be- 

 tween the embryonic and mature forms. A 

 third corpuscle is without a nucleus and is sim- 

 ply a differentiated portion of the protoplasm of 

 the vessel walls. These are the true red corpus- 

 cles. Briefly, then, there are four stages in 

 corpuscle development the original nucleated 

 red corpuscle, the stage of the same in which 

 the nucleus is markedly granular and the pro- 

 toplasm increased, the embryonic or amphibian 

 form, and the final true non-nucleated red cor- 

 puscle ; the white cells appear between the second 

 and third stages. 



The problem of the coagulation of blood recog- 

 nizes three factors as having a part in the op- 

 eration, viz., a coagulable material, a ferment, 

 and certain salts. Investigation has been pre- 



