TRANSACTIONS OF THK SECTIONS. 91 



cells ; but it is questionable whetlier they are anjTvise essential to the gi'owth and 

 well-being of the plants, and are not rather tlie results of disease, depending on a 

 state of the fluids, somewhat analogous to that which in animals is favourable to the 

 production of calculi. It would be foreign to my piu'pose to express any opinion as 

 to the great question whether, in the vital economy, the forces m action are merely 

 physical forces, or, admitting, as must be admitted, that these forces are concernecl 

 in the phenomena of life, whether something more is not required, a special force, 

 a vital force, to give them direction, or modify their influence. 



Note on an Addition to the Sphygmograph. By Dr. Balthazar W. Foster. 

 After describing the construction and application of Marey's Sphygmograph, the 

 author pointed out that the screw regidating the amount of pressm'e exerted- on the 

 artery under examination required adjustment for nearly every case. Too great 

 pressure often materially altered the form of the pulse ti-ace"; and as it is essential for 

 accuracy in comparative observations that the pressure on the vessels should be the 

 same, the author stated that by having an index attached to the pressure-screw, 

 and a graduated circle described round the screw as a centre, the position of the 

 index woidd always enable the obsei-ver to exercise the same amount of pressure 

 in any number of cases. 



On a Peculiar Change of Colour in a Mtdatto. By Dr. Balthazar W. Foster. 



After alluding to the present state of our knowledge of the conditions connected 

 with the development of pigment, the author related an instance in which he had 

 observed a gradual disappearance of the cutaneous pigment in a Mulatto aged 43. 

 Minute white spots first appeared on the man's back, and by coalescing gradually 

 formed large white patches. These constantly extending, in the com-se of six 

 years the whole of the trunk became perfectly white, spots of the original colour 

 remaining onlj- on the extremities. The face retained its dark hue, and an irre- 

 gular margin encircling the neck formed the limit of the upward advance of the 

 white colom-. Isolated spots of white had appeared, however, on the forehead and 

 at the angles of the jaw. The white skin was perfectly healthj" in appearance and 

 not to be distinguished from that of a European. The man's hair was black and 

 crispy, and of a flattened elliptical form on section. Blisters applied to the bleached 

 surface restored the dark colour in in-cgular spots, which remained unchanged for 

 several months. No discoverable condition in the man's constitution or habits 

 could be regarded as the antecedent of the remarkable change, except possibly a 

 very weak and sluggish state of the circulation. A series of large photographs 

 illustrated the communication. 



On the Action of Carhonic Oxide on the Blood. By Dr. A. Gamgee. 



When carbonic oxide is passed through venous blood it acquires a persistently 

 florid colour, which was first pointed out by Claude Bernard, and the colouring- 

 matter, although it possesses a spectrum identical with that of ordinary blood, is 

 distinguished from it by not yielding, when treated with reducing agents, the spec- 

 trum first described by Stokes as that of reduced or purple cruorine. This pro- 

 perty of carbonic -oxide blood was first published by Hoppe. As a result of his 

 own investigations, Dr. Gamgee has found : — First, that the peculiar compoimd of 

 carbonic oxide and blood colouring-matter is formed even when the latter has 

 been reduced, and is still in the presence of a large excess of a reducing solution. 

 Secondly, that when the compoimd of carbonic oxide and colouring-matter is 

 treated with acetic <acid, whilst hsematine is formed, carbonic oxide is disen- 

 gaged. Thirdly, that carbonic oxide, besides modifying the optical properties 

 of the colouring-matter of blood, affects in a remarkable manner the point at 

 which it coagulates, so that, under its influence, an almost perfect separation of 

 the hremotogiobulin (using the term to express the normal colouring-matter of 

 the blood) from the albumen may be eftected. Normal ox's-blood, when diluted 

 with nine times its volume of water, becomes tiu-bid at 145° Fahr., and when the 

 temperature has reached 172^ Fahr. its colour is completely destroyed. If such a 



