1881.] Dr. H. E. Roscoe. Note on Protagon. 



35 



digastric muscles, and the strain on their central parts, as explained 

 above, leads to the disappearance of muscular fibre in the neighbour- 

 hood of the tendinous insertion, which accordingly becomes a tendon 

 uniting two fleshy bellies. On the other hand, in most of the Mam- 

 malia, the usual attitude is prone, and the cavity of the mouth, when 

 the food is being swallowed, is in a line with the oesophagus, or nearly 

 so ; in such a position the mylo-hyoid and genio-hyoid muscles can act 

 effectively in elevating and drawing the hyoid bone forwards, and 

 deglutition is effected without the aid of the digastric muscles, which 

 are accordingly simple and unconnected with the hyoid, as in the 

 dog ;* or, if intersected, the tendinous band is either the origin of a 

 raphe continued inwards, as described in Gynmura and Upomopliorus 

 (which may be, as in these genera, wholly unconnected with the hyoid), 

 or the rudiment of such in an ancestral form. 



IV. " Note on Protagon." By Henry E. Roscoe, LL.D., F.R.S. 

 Received March 16, 1881. 



In his communication to the Royal Society of January 6th last, on 

 the subject of the presence or absence of potassium in protagon, 

 Dr. Thudichum endeavours to raise an entirely false issue. The 

 question I had to decide was not whether protagon contains a trace of 

 potassium, but whether, to quote Dr. Thudichum's own words, it con- 

 tains " no less than 0*76 per cent, of potassium." In the first instance 

 I endeavoured to settle this matter by spectroscopic investigation, and 

 employed two samples of protagon which had been prepared under 

 Dr. Gamgee's direction in the course of the research of which he com- 

 municated the results to the Royal Society. In one of these samples, 

 which had been four times crystallized, I was unable to det3ct any 

 potassium ; the quantity of the body at my disposal was however 

 small, as the rest of the specimen had been employed in previous 

 work, and Dr. Gamgee placed in my hands a large sample of protagon 

 only twice crystallized, which had been prepared by Dr. Blankenhorn 

 under his direction, and it was an analysis of this latter specimen 

 which I communicated to the Royal Society. As stated, I estimated 

 by spectroscopic means the amount of potassium present in 1 grin, of 

 the substance to be of a milligram, that is, 0'005 per cent. To 

 these observations of mine, Dr. Thudichum replied by a paper entitled 

 " On the Modifications of the Spectrum of Potassium which are 

 effected by the presence of Phosphoric Acid, and on the Inorganic 



* The difficulty experienced by a dog in swallowing when the head is bent for- 

 wards is well known to every one who has seen one attempting to swallow even 

 a moderate sized morsel when seated erect in the familiar attitude known as " beg- 

 ging." 



D 2 



