96 



SCIENCE. 



[N. S. Vol. II. No. 30. 



gaseous exchanges occurring in the lungs 

 of air-breathing animals are not due to 

 purely physical causes, such as different 

 partial pressures of the gases, but to a true 

 process of secretion and excretion. 



Very considerable progress has been made 

 in unravelling the intricate mechanism of 

 the brain and spinal cord, and this has been 

 accomplished mainly by the application of 

 the Wallerian method of studying the de- 

 generations that follow section of various 

 strands of nerve fibres or destruction of gray 

 matter. Mott has given experiments that 

 support Munk's original conclusion that the 

 motor area on the cortex of the cerebral 

 hemispheres is also connected with sensa- 

 tions of touch and pressure, and is not solely 

 for the emission of motor impulses, or, in 

 other words, that the mechanisms for sen- 

 sation and touch and for motor impulses 

 are closelj' related in the brain. Bayliss, 

 Bradford, Boyce, Sherrington, Langiej'^ and 

 Anderson in this country have also investi- 

 gated the convexions of the various spinal 

 nerves with the great plexuses or networks 

 from which issue the main nerves of the 

 limbs, and thus physiologists are slowlj' ac- 

 cumulating knowledge that will by-and-by 

 be of great value to the physician. It 

 wUl be possible to correlate sensations in 

 various areas in the skin and various 

 muscular movements with certain nerve 

 roots and with certain portions of the spinal 

 cord. In other words, a new physiological 

 anatomy will be established by experiment 

 and facts will be discovered that could 

 never be laid bare by the scalpel. The 

 most notable advance, however, in nervous 

 physiology has been made by Gustav Mann, 

 of Edinburgh, who, following the lead of an 

 American observer, has demonstrated ma- 

 terial changes following the stimulation of 

 nerve cells in the sympathetic ganglia, iu 

 the cord, and even iu the brain itself. 

 Under stimulation the cells appear to swell 

 and to become clearer owing to a peculiar 



matter tei'med chromatin being used up. 

 In this way even long continued stimulation 

 of the retina bj' light has been found to 

 cause changes, Adsible to the microscope and 

 depicted by photography, in the nerve cells 

 of the part of the brain which is the seat of 

 the conscioiisuess of Adsion. 



Numerous researches have been made on 

 the functions of the liver, kidney, pancreas 

 and spleen, all going to show that these or- 

 gans are not related only to one or even 

 two individual functions, but that each or- 

 gan is the seat of complex metabolisms, or 

 changes of which the obvious secretion is 

 only the outward expression. Thus, the 

 liver not merely secretes bile and forms 

 glycogen, but it also has important anti- 

 toxic powers by which poisonous matters, 

 formed possibly in the intestines and car- 

 ried thence to the liver, have their effects 

 counteracted. The organ is also concerned 

 in the decomposition of proteids and even 

 iu the transformation of fats. In like 

 manner the kiduej'S and the pancreas have 

 intestinal functions, the nature of which is 

 still obscure to physiologists. Lastly, the 

 selective actions of epithelial cells are re- 

 ceiving greater attention, and it is found 

 that these play an important part in many 

 vital phenomena. By the activities of these 

 cells physical operations, such as the pas- 

 sage of certain sxibstances through mem- 

 branes, are so modified as to make it im- 

 possible, in the present state of science, to 

 regard them as purely physical. A molec- 

 ular phj'siology of the future maj' demon- 

 strate that they are trulj' physical, but at 

 present the vitality of the tissues involved 

 is an unexjjlained factor in the process. 



In the field of physiological acoustics the 

 phonograph promises to be an instrument 

 valuable in research. Soon after its inven- 

 tion the tinfoil phonograph was used suc- 

 cessfully by the late Professor Fleeming 

 Jenkin and Professor Ewing (now of Cam- 

 bridge) iu the investigation of vowel sounds, 



