1876.] 



On the Photographic Spectra of Stars. 



445 



the lateral portion of the rectus abdominis muscle and the abdominal 

 portion of the pectoralis major muscle. 



As to the tongue, it seemed to me that having here a more compli- 

 cated organ, supplied with so many more nerves than a simple muscle, 

 and one that had been already frequently examined without much success, 

 it was not so suitable to the object in view. Erom the few experiments, 

 however, that I have made on this organ, it seems to me that stimula- 

 tion of the glossopharyngeal nerve, rather than the hypoglossal, causes 

 dilatation of its vessels. 



In concluding this short sketch of my experiments I would venture to 

 say that as, from my own observations, stimulation of the anterior crural 

 nerve of dogs causes dilatation of the vessels in that group of muscles 

 known by the name of quadriceps extensor, while Sadler has shown the 

 same for the biceps and semitendinosus muscles and for the flexor com- 

 munis digitorum of the forearm, and as, in frogs, stimulation of their 

 respective nerves causes dilatation of the vessels in the mylohyoid, pec- 

 toralis major, and rectus abdominis muscles, it is reasonable to suppose 

 that this holds good for simple voluntary muscles throughout the body. 



I would further add that the beauty of the circulation and the extent 

 of the dilatation that may be observed in the arteries of the mylohyoid 

 muscle lead one to hope that further investigations here may materially 

 assist in solving the vexed question, " What is the mechanism by which 

 dilatation of a vessel is caused ? " 



All the foregoing observations on the circulation in the muscles of the 

 frog were carried on in the Physiological Laboratory of the University of 

 Cambridge. 



lY. " Note on tlie PhotograpMc Spectra of Stars. By William 

 HuGGiNs, D.C.L., LL.D., F.R.S. Eeceived December 6_, 

 1876. 



In the year 1863 Dr. Miller and myself obtained the photograph of 

 the spectrum of Sirius. 



" On the 27th January, 1863, and on the 3rd March of the same year, 

 when the spectrum of this star (Sirius) was caused to fall upon a sensi- 

 tive collodion surface, an intense spectrum of the more refrangible part 

 was obtained. Prom want of accurate adjustment of the focus, or from 

 the motion of the star not being exactly compensated by the clock 

 movement, or from atmospheric tremor, the spectrum, though tolerably 

 defined at the edges, presented no indications of lines. Our other inves- 

 tigations have hitherto prevented us from continuing these experiments 

 further ; but we have not abandoned our intention of pursuing them " *. 



I have recently resumed these experiments by the aid of the 18-inch 

 ^ Phil. TtcaM. 1864, p. 428. 



2x2 



