Sept. 26, 1872] 



NATURE 



447 



tile time 'in emptying itself, but it is only double that time, 

 which demonstrates the statement. 



A complete logical explanation of the action of the pnenmo- 

 gastiic can be given on this theory, by assuming that its func 

 tion consists in diminishing the caUbre of the small arteries of 

 tlie coronary system, and always keeping them somewhat 

 contracted. 



PHENOMENA OF COAGULATION JN 

 FROG'S BLOOD* 



T WAS endeavouring in the autumn of last year, at Prof. 

 Sanderson's instigation, to demonstrate upon the frog some 

 of Briiche's fundamental experiments on the coagulation of the 

 blood, which he performed on the tortoise ; I was surprised at 

 the apparent failure of some of them. For instance, having tied 

 a glass tube into the animal's aorta an \ allowed it to fill with 

 blood, I expected that which was in the tube speedily to coagu- 

 late, that which remained in the heart to continue liquid for a 

 considerable time. But no such contrast was observable, both 

 portions of blood remained perfectly fluid for an indefinite time. 

 I say appare.ritly, for, in fact, on subsequently turning out the 

 blood, a slight film of coagulated fibrin w.as observable attached 

 to the walls of the tube. Of course the corpuscles being the 

 heavier gravitate to the bottom, and the blood thus becomes 

 divided into two portions, a clear fluid above and a mass of red 

 corpuscles below, with a thin filmy stratum of white again on the 

 surface of the latter. 



To show that the clear fluid is plasma and not merely serum, 

 that is to say, that it fully retains its coagulability, it is sufticient 

 to take a little up into a very fine, almost capillary, glass tube. 

 The extent of surface to which it is thus exposed very quickly 

 determines its coagulation. 



Following up the subject still further, I found the same thing; 

 to happen when the blood is allowed to drop into a glass vessel, 

 the whole remaining fluid, except that portion in immediate con- 

 tact with the sides, the corpuscles subsiding as before, and the 

 supernatant liquid being readily coagulable in a capillary tube. 



But frog's blood does not always behave in this manner. It 

 is not unfrequently the case, especially at this season of the year, 

 that the blood of these animals beh.aves to all appearance 

 precisely as we are in the habit of expecting that blood should 

 behave, that is to say, the commencing subsidence of the cor- 

 puscles is arrested, the fluid solidifies, seemingly throughout. 

 And, indeed, in rare instances, the coagulation is complete to 

 the centre, and the mass soon separates into clot and serum, 

 which latter, in these cases, never yields a coagulum in a capillary 

 tube. More frequently, however, on breaking the surface with 

 a knife, the interior of the coagulated mass is seen to be occupied 

 by still fluid blood. 



In either case, the coagulated fibrin soon begins to contract ; 

 and this contraction proceeds to such an extent that not only is 

 the serum of the blood expressed from it, but it comes to pass 

 that there is no longer room in its meshes for the involved cor- 

 puscles, which consequently begin to be squeezed out and to fall 

 to the bottom of the glass. This diminution in volume of the 

 clot may proceed so far that in the course of a few hours the 

 blood may present an appearance precisely as if it had not un- 

 dergone coagulation at all, there being a mass of corpuscles at 

 the bottom of the vessel, and a clear supernatant fluid. The 

 contracted remains of the clot may however be always found, 

 although often obscured by the liberated corpuscles. Now, this 

 disappearance of the clot of frog's blood under certain circum- 

 stances was noticed some years ago by v. Reclinghausen, and 

 a-cribed by him to are-liquefaction of ihe fibiin ; and not un 

 r.atuially, if we consider the astonishing diminution in bulk 

 wliich it undergoes, and the fact that the serum in such cases is 

 fr<(|uently found to yield a further coagulum. 



But in every case of the latter kind, i.e. in every case in which 

 the supernatant fluid yields a coagulum in a capillary tube, it 

 will have been found that the primary coagulation was incom- 

 plete, i.e. that the central pans of the blood remained fluid, 

 whereas on the other hand it is certain that when the primary 

 coagulation has been complete, no lui ther coagulum is Li'er 

 obtainable, although, in this case al^o, the clot may have con- 

 tracted to a relatively exceedingly small bulk, in fact, may have 

 almost disappeared. 



A further proof, if one were needed, that the diminution of the 



*iPaper read before the British Association at Brighton in Section D. 

 (Department of Anatomy and Physiology), by E. A Schafer, M B. 



clot is due merely to contraction and not re-liquefaction of fibrin, 

 is to be found in the examination under the microscope, using an 

 immersion objective, of the process as it occurs in a very thin 

 walled and fine capillary glass tube. 



The phenomena here observed are wholly those of contraction; 

 first simply serum, then white corpuscles, and finally red cor- 

 puscles being expressed, until a mere thread of fibrin remains, 

 almost obscured by the corpuscles and still including a few. 



Throughout the whole proce>s, however, there is no tiace of 

 a re-liquefaction ;of fibrin ; this would of course involve the 

 dropping away of the corpuscles from ihe sides ; on the contrary, 

 they are most evidently squeezed out, some of them being 

 actually ruptured in the passage and appearing on the exterior 

 of the clot as sm.all reddish spheioids. The facts then, briefly, 

 are these : that frog's blood, especially if taken during the winter 

 months, exhibits but very little tendency to coagulate, with the 

 exception of the portion in immediate contact with a 

 foreign surface; that, when apparently coagulated through- 

 out, the central portions are very apt to remain fluid, and to 

 impart coagulability to the expressed serum ; that the clot when 

 formed frequently tends to attain a relati>ely very small bulk ; 

 and, finally, that this diminution in bulk is due to contraction 

 merely, not re liquefaction of the fibrin. 



PHYSICS 



Acoustic Experiments on the Seine during the Siege 



of Paris 



In the experiments made by Colladon and Sturm on the Lake 

 of Geneva, in 1S27, to determine the velocity of sound in water, 

 the source of sound was a bell, weighing sixty-five kilogrammes, 

 fixed to a boat immersed in the water near RoUe. -Vnother 

 boat, moored near Thonon, carried the observers, who employed 

 a long acoustic tube made of metal, one extremity of which, 

 widened and closed with a membrane, was thrust into the water. 

 The distance from RoUe to Thonon is about 13,500 metres, so 

 that the range of the sound was considerable. The water in 

 that part of the lake is of great depth. 



During the siege of Paris, the idea arose of establishing an 

 acoustic telegraph by means of the Seine, between the invested 

 city and provinces that had not been invaded. The Geneva ex- 

 periments appeared to favour the proposal. 



M. Lucas was charged by the Mhiister of Public Works to 

 make some experiments on the subject, which he accordingly 

 did in November, 1S70. He gives an account of these to the 

 Paris Academy. 



In the first series, a bell weighing forty kilogrammes was 

 lowered by a windlass from the bow of a barge, to a position 

 twenty or thirty centimetres from the bottom. It contained a 

 clapper, which was moved by means of wires carried up to the 

 barge. Two workmen were charged to ring the bell at certain 

 fixed intervals, while the observers, in another boat, marked the 

 efifect at different distances, being carried along by the current. 

 The acoustic tube employed was i'5oni. long, and the membrane 

 e>f its orifice, immersed in the water, was turned towards the 

 bell. At the distance of a few metres, a dull sound was heard 

 (like that of a drum beat with a drum-stick), at each stroke given 

 to the bell. The intensity diminished with the distance, and 

 the sound ceased to be perceptible at about i,Soo metres. The 

 result was constant for experiments repeated at different parts of 

 the river. 



In a second series of experiments, a bronze bell, weighing 354 

 kilogiammes, was used. This was hung in a wooden franse 

 weighing 446 kilogrammes, constructed in the form of a quad- 

 rangular pyramid. The hammer of the bell weighed sixteen 

 kilogrammes, and was moved by wires, as in the other case. The 

 frame and bell were suspended by chains from the (our corners, 

 between two barges, and then lowered into the water. The 

 mode of observation was the same as in the former case. 



A few metres from the barge a slight metallic sound was heard, 

 doubtless from the acoustic tube vibrating with the membrane. 

 The sound soon became dull, its intensity decreased rapidly with 

 the distance ; at 1,400 or 1,500 metres there was no perception 

 of it. 



Comparing these expeiiments with those of the first series, we 

 have the unexpected result that the very intense sound of a bell 

 weighing 354 kilogrammes has a less range than the weaker 

 sound from a bell of forty kilogrammes. 



In a third series, a small bell, twelve centimetres diameter, 

 was sounded in the water alternately with the bell of forty kilo- 



