286 



Mr. H. T. Brown on the 



[Mar, 17, 



The tricuspid is evidently abnormally large in relation to the mitral 

 orifice. 



If we suppose the other three orifices to be nearly normal (and it is 

 evident that the pulmonic and aortic bear their normal relation to one 

 another), we can calculate the excess of dilatation exhibited by the tri- 

 cuspid opening 



T_P 

 M~A J 



.-. T = l-15 x — =1-42 sq. inch. 

 •79 4 



Hence the tricuspid is *58 inch in excess of its normal area, or mere than 

 one-third of its proper size in excess. 



5. Bronchitis (Dr. Peacock). 



The heart in this case weighed eleven ounces. As this does not much 

 exceed its usual weight, it is clear that the pulmonic obstruction was 

 slight. "We should therefore expect to find but little deviation from the 

 "law of the orifices." 



Tricuspid 62 lines. 306 sq. lines. 



Pulmonic 45 161 



Mitral 54 232 



Aortic 39 121 



T_306 ,_ 

 M 232 d - 



I= l61 = l-33 

 A 121 _ 



D inference of the ratios = '01 



This result fullv bears out the inferences above made. 



II. " On the Estimation of Ammonia in Atmospheric Air." By 

 Horace T. Brown, Esq. Comnmuicated by Dr. Fraxkland. 

 Received February 19, 1870. 



In the attempts that have been hitherto made to estimate the ammonia 

 present in atmospheric air, the results arrived at by the various experi- 

 menters have differed so widely that it is still a matter of uncertainty what 

 the quantity really is. That it is a very small amount all agree, but the 

 extreme results on record vary as much as from 13*5 to '01 part of car- 

 bonate of ammonium per 100,000 of air. It may therefore not be without 

 interest to give an account of a simple method affording very concordant 

 and, I believe, accurate results, at the same time being easy of performance 

 and requiring but little time for an experiment. 



The apparatus used consists of two glass tubes, each of about 1 metre 



