2 -.6 



NA TURE 



[January 3, 189- 



country, the fisheries. Much has already been done in 

 Canada in the miller of the propagation of food fishes but 

 much yet remain; to be done in investigating the conditions 

 of the fisheries of both salt and fresh waters, and it may no* 

 be anticipated that before many years an important basis of 

 fact will hare been built up upon this subject. 



One important line of inquiry must yet be mentioned in 

 which no systematic beginning has been made, either under the 

 auspices of the Government or by any society or institution 

 especially devoted to it. This is the field of ethnology, which 

 in Canada is a very extensive one, and which calls for imme- 

 diate effort, inasmuch as the native races, with which this study 

 is concerned, .nre either rapidly passing away or are changing 

 from their primitive condition. 



Ten years ago, the Council of the British Association 

 was so much impressed with the urgency of investigations 

 of this kind, that it not only appointed a committee to 

 deal with the subject, but has since given e.tch year a sub- 

 stantial grant from its own funds in aid of this work. The 

 Canadian Government for several years supplemented this 

 grant, and eight reports, filled with valuable observations on 

 the western tribes, have so far, as a result of this action, been 

 published in the annual reports of the .Association. It has been 

 decided, however, that the functions of the committee, with 

 the grant accorded by the Association, shall cease this year, so 

 that if further progress is to be made, the matter must now be 

 taken up by the Canadian Government. It is earnestly to be 

 desired that the Government may at least contemplate the at- 

 tachment, either to the Indian Department or to some other 

 department, of a properly qualified ethnologist, by whom these 

 investigations may be continued. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, December 6, 1894. — "Experimental Re- 

 searches on Vegetable Assimilation and Respiration. No. I. 

 On a New Method for Investigating the Carbonic Acid 

 Exchanges of Plants." By F. F. Blackman, B.Sc, Demon- 

 strator of Botany in the University of Cambridge. 



This paper consists of a description of a complicated apparatus 

 for the estimation of very small amounts of COo, which is 

 especially adapted for biological research. 



By its aid the evolution of C< >._, by a single germinating seed, 

 or by a small area of a foliage leaf, can be accurately estimated 

 from hour to hour without a break, for any desired time, while 

 for the same area of leaf the more active absorption of CO„ in 

 assimilation can be easily determined for such short periods of time 

 as fifteen minutes, and that at the same time separately for the 

 two surfaces of one and the same leaf area. Further, for the 

 purposes of this assimilation, air containing any proportion of 

 COj, however small, can be supplied continuously to the tissue 

 under investigation. The apparatus is practically in duplicate 

 throughout, and strictly comparative double experiments can be 

 pcrfoimed. 



The experiments are carried out in a continuous current of 

 air at atmospheric pressure ; the actual estimation of the COo 

 is accomplished by leadingthis through barylasolution, of which 

 only a small quantity is used in each case, and the whole of it 

 afterwards titrated in iitii in the absorption tube, to which only 

 air freed from CO.. is otherwise admitted. 



The following communication illustrates the applicability of 

 this apparatus to theinvestigatiun of minute quantities of carbon 

 dioxide : 



No. II. "On the Paths of Gaseous Exchange between 

 .\erial Leaves and the Atmosphere." 



CDiieliisicins. — (1) That if the amounts of CO, evolved in 

 respiration by the two surfaces of any leaf area be determined, 

 it will be found that there is a very close relation between these 

 amounts and the distribution of the stomala. In those Ic.tvcs 

 with no stomata on the upper surface, practically no COj is 

 exhaled from that surface, and all escapes from the lower sur- 

 face. When stomata occur equally on the two surfaces the 

 amounts of CO^ exhaled are equal on the two surfaces, and 

 so on. 



(2) Similarly with assimilation, no CO.j is absorbed by an 

 aitomi'iferouH leaf surface, and when stomata occur on both 

 surf.ices, then the amounts absorbed follow the ratios of stomatic 

 distribution. 



(3) Buussingault's experiments on the assimilation of leaves 



NO. I314, VOL. 51] 



with blocked stomata, which h-tve hitherto formed the mainstay 

 of the "cuticular" absorption theory, are completely viliateil 

 by having been performed in super-optimal percentages of CO.,, 

 Their interpretation is exactly the reverse of that usually 

 accepted. 



(4) The exhalation of CO2 in bright light by a leafy shoot in 

 Garreau's well-known experiment, is not the expression of any 

 physiological truth for the leaf, but is only due to the presence 

 of immature parts, or of tissues not sufficiently green, or not 

 fully illuminated. Mature isolated green leaves fully illuminated 

 assimilate the whole of their respiratory CO,,, and allow none 

 to escape from them. 



December 13, 1S94. — " The Influence of the Force of Gravity 

 on the Circulation." By Prof. Leonard Hill, M. B. 



The chief results of the research are contained in the follow- 

 ing conclusions : — 



(1) That the force of gravity must be regarded as a cardinal 

 factor in dealing with the circulation of the blood. 



(2) That the important duty of compensating for the simple 

 hydrostatic effects of gravity in changes of position must be 

 ascribed to the splanchnic vaso-motor mechanism. 



(3) That the effects of changing the position afford a most 

 delicate test of the condition of the vaso-motor mechanism. 



(4) That the amount of compensation depends largely on 

 individual differences. 



(5) That the compensation is far more complete in upright 

 animals such as the monkey, than in rabbits, cats, or dogs, and, 

 therefore, is probably far more complete in man. 



(6) That in some normal monkeys over-compensation for the 

 hydrostatic effect occurs. 



(7) That in the normal monkey and man gravity exerts but 

 little disturbing inrtuence, owing to the perfection of the com- 

 pens.itory mechanism. 



(8) That when the power of compensation is damaged by 

 paralysis of the splanchnic vasoconstrictors, induced by 

 severe operative procedures or by injuries to the spinal cord, 

 by asphyxia, or by some poison such as chloroform or 

 curare, then the influence of gravity becomes of vital import- 

 ance. 



(9) That the feet-down position is of far greater moment than 

 the feet-up position, because when the power of compensation 

 is destroyed the blood drains into the abdominal veins, the 

 heart empties, and the cerebral circulation ce.ises. 



(10) That, generally speaking, the feet-up position occasions 

 no ill consequence. 



(11) That the horizontal and feet-up positions at once abolish 

 the syncope induced by the feet-down position by causing the 

 force of gravity to act in the same sense as the heart, and thus 

 the cerebral circulation is renewed. 



(12) That firmly bandaging the abdomen has the same effect. 

 While the heart remains normal, and so long as the mechanical 

 pressure is applied to the abdominal veins, the blood pressure 

 cannot possii>ly fall. 



(13) That if the heart is affected, as by chloroform or curare 

 poisoning, the restoration of pressure is incomplete, and it is 

 possible that the heart may be slopped altogether by the inrush 

 of a large quantity of blood, caused by too rapid an applica- 

 tion of pressure on the abdomen. More work would be thrown 

 upon the heart than, in its impoverished conditioi;, it could 

 perform. 



(14) That vagus inhibition and cardiac acceleration are sub- 

 sidiary compensatory mechanisms in the feel-up and feel-dowa 

 positions respectively. 



(15) That chloroform rapidly paralyses the compensatory 

 va.so-molor mechanism, and damages the heart. 



(16) That ether, on the other hand, only paralyses the com- 

 pensatory va^-o-motor mechanism very slowly and when pushed 

 in enormous amounts. 



(17) That the vaso-motor paralysis induced by these ana:s- 

 ihetics lasts for some considerable time after the removal of the 

 an.TJSthelics. 



(18) That chloroform can, by destroying the com])cnsalion 

 for gravity, kill the animal, if it be placed with the abdomen oa 

 a lower level than the heart. 



(19) 'I'h.at elevation or compression of ihe abdomen imme- 

 dialcly compensates for the vaso-motor paralysis produced by 

 chloroform. 



(20) That compression or elevation of the abdomen, coupled 

 with artificial respiration and with squeezing of the heart 

 through Ihe thoracic walls, is the best means of restoring an 



