478 



Prof. J. B. Haycraft. On the Action of a [Apr. 3, 



shorter wave-length. ; but as the spark lines of iron seem to be quite 

 as strongly depicted on the plates in regions of the spectrum far 

 above T as they are in the regions below, we think that want of sensi- 

 tiveness in the plates cannot be the only reason for the absence of 

 higher lines, but that the emissive power of the metals for these lines 

 is feeble at the comparatively low temperature of the flame. 



This supposition accords with what we have observed of the lines 

 seen in a carbon tube heated by the electric arc (" Proc. Camb. Phil. 

 Soc," iv, 263). The iron lines photographed as reversed against the 

 hot walls of such a tube were at certain stages of temperature the 

 same, speaking generally, as those we have noticed in the flash of 

 the detonating gases ; but as the temperature of the carbon tube rose, 

 more refrangible lines, including all the strong iron lines in the 

 neighbourhood of T, the lines of aluminium near S, and the mag- 

 nesium line X 2852, were reversed in the photographs. 



Gouy (" Comp. R.," 1877, p. 232), using a modification of Bunsen's 

 burner fed with gas mixed with spray of metallic salts, observed at 

 the point of the inner green flame three or four iron lines which we 

 have not observed in the flame of the detonating gas, the lines Z? x and 

 5 2 of magnesium, two cobalt lines in the blue which we have not seen, 

 one line of zinc, and one of cadmium, and the two strong green rays 

 of silver. Can the appearance of these rays under these circumstances 

 imply that the temperature of the inner green cone of a Bunsen 

 burner, when the proportion of air to coal-gas is near the exploding 

 point, is higher than that of the explosion of hydrogen and oxygen ? 



The interesting theoretical questions which are suggested by the 

 facts recorded in this paper we must leave for future discussion. 



IV. " On the Action of a Secretion obtained from the Medi- 

 cinal Leech on the Coagulation of the Blood." By John 

 B. Haycraft, M.B., F.R.S. (Edin.), Professor of Physi- 

 ology in the Mason and Queen's Colleges, Birmingham. 

 Commnnicated by Dr. Lauder Brunton, F.R.S. Received 

 March 28, 1884. 



The following is an offshoot from a more extended investigation 

 upon the coagulation of the blood not yet ready for publication. 



The blood flowing from a leech-bite is not readily stopped, often 

 flowing for upwards of an hour after the animal has been removed. 

 The blood within the body of the creature remains fluid for an 

 indefinite time ; and when ejected it is found to have lost its 

 coagulability. These are facts known to every surgeon, but they 

 have received no explanation. 



While endeavouring to solve one very difficult problem, " why the 



