

654 



PHYSIOLOGY. 



variations in some of the details of the opera- 

 tion, which he pointed out and described. Prof. 

 Christian! rebutted Prof. Munk's interpretation 

 of his experiments, maintained at all points the 

 validity of the results he had arrived at, and 

 referred to a more complete account and vin- 

 dication of them which was shortly to be pub- 

 lished. 



Eesearches have been made by Dr. M. E. 

 Holbrook into the termination of nerves in the 

 liver. He examined with the microscope the 

 livers of various animals, as well as one of a 

 child and oue of an adult, employing a combi- 

 nation of chloride of gold with formic acid as 

 his reagent. The nerves appeared marked by 

 a large number of nuclei, by the presence of a 

 delicate sheath around each fiber, and by the 

 dark violet color they had taken on from the 

 reagent and the carmine staining. On the 

 border of the lobules the nerves, which were 

 still in bundles of from three to five or more, 

 ramified and entered the lobule in different 

 places, mostly branching at acute angles along 

 the capillary blood-vessels. Further, the fibril- 

 Ise of the nerves course along the layers, or 

 rims of cement substance, which have been 

 found to separate the liver epithelia in the 

 same manner as all other epithelia and endo- 

 thelia are separated from each other. The re- 

 sults of Dr. Hoi brook's researches are in ac- 

 cordance with M. Nesterowsky's assertions, 

 that the blood-vessels of the liver, both the 

 large vessels of the porta and the capillaries 

 within the lobe of the lobule, are accompanied 

 by filaments of nerves; but in none of his 

 large number of specimens has he ever been 

 able to trace a nerve-filament penetrating into 

 an epithelium, as is claimed to occur by E. 

 Pfluger. 



Single induction shocks applied to the me- 

 dulla or spinal cord, when the connection be- 

 tween these and the brain is severed, have been 

 found by H. Kronecker and E. Nicolaides, in 

 experiments on dogs and rabbits, to have no 

 effect, or only a slight effect, even when the 

 shocks were destructively strong, upon blood- 

 pressure. When moderately strong stimuli were 

 used, there was no summation of their effects 

 until the separate shocks succeeded each other 

 at least two or three times in one second. This 

 slow rate of stimulation produces a greater 

 effect in raising blood-pressure when the in- 

 tensity of the single shock is increased. But 

 the strongest stimuli of slow rate produce far 

 less increase in blood - pressure than stimuli 

 of moderate strength and greater frequency. 

 When the intensity remains constant, increase 

 in frequency of stimulation raises blood-press- 

 ure, but the maximum is reached when from 

 twenty to thirty stimuli per second are pro- 

 duced. After the stimulation is brought to a 

 close, the blood-pressure returns to its normal 

 level. 



Dr. W. H. Gaskell, experimenting with the 

 nerves of a crocodile to test the supposition 

 that the sympathetic system might provide 



the heart entirely with augmentor fibers 

 while the vagus contained only inhibitory, 

 found that stimulation of the nerves branch- 

 ing from the main sympathetic chain increased 

 the rate of cardiac rhythm, and augmented 

 the force of the -auricular contractions; while 

 stimulus of the vagus slowed the rhythm 

 and diminished the strength of the auricular 

 contractions. Carrying his experiments to the 

 frog, while the effects of stimulation of the 

 ordinary vagus trunk were as already de- 

 scribed, he obtained most striking and decisive 

 results from stimulation of the sympathetic on 

 the one hand, and of the intra-cranial vagus on 

 the other hand. Stimulation of the sympa- 

 thetic before its entrance into the combined 

 ganglion of the sympathetic and vagus pro- 

 duced purely augmentor effects ; and stimula- 

 tion of the vagus within the cranial cavity, be- 

 fore its entrance into the ganglion, produced 

 purely inhibitory effects. 



The affections of the nervous system pro- 

 duced by the presence in the body of certain 

 metals, such as lead and mercury, have not 

 been sufficiently studied to determine whether 

 the action of the poison is upon the peripheral 

 or the central apparatus. Dr. Popow has been 

 studying the subject on animals (mainly dogs) 

 poisoned by arsenic, lead, and mercury, re- 

 spectively, administering the poison in most 

 cases in varying quantities, in order to contrast 

 the effects of acute and chronic poisoning. 

 The general result of his inquiry goes to show 

 that marked changes of an inflammatory char- 

 acter occur in the spinal cord, both in the gray 

 and white matter, under all these conditions. 

 In acute arsenical poisoning, the cord was soft- 

 ened, the gray matter especially being red- 

 dened and swollen ; there was proliferation of 

 the nuclei of the blood-vessels, and an exuda- 

 tion of a peculiar hyaloid substance. The 

 nerve-cells were swollen, their processes dwin- 

 dled, and their protoplasm became granular or 

 vacuolated, while in the white columns the 

 axis cylinders showed irregular thickenings. 

 In chronic poisoning it was difficult to dis- 

 criminate between the two portions of the 

 cord, the divided surface having a yellowish- 

 red color throughout ; the walls of the vessels 

 were thickened, and hyaline masses abounded ; 

 the nerve-cells were vacuolated or shrunken 

 and pigmented; while free pigment masses, 

 representing traces of hemorrhage, occurred 

 throughout the sections. Very similar changes 

 were observed in the spinal cord after poison- 

 ing by lead and mercury respectively. In 

 each instance the peripheral nerves and the 

 nerve-roots showed no alteration ; the con- 

 clusion, therefore, is that the paralysis, spasms, 

 etc., characteristic of the toxic effects of these 

 metals, depend upon a central rather than a 

 peripheral disturbance, all the degenerative 

 changes described as occurring in nerves and 

 muscles being strictly secondary effects. 



The Circulatory System. Dr. D. J. Hamilton, 

 of the University of Aberdeen, has communi- 



