16 



Among bars of the latter kind, it was found that it was only in the 

 case of bismuth and antimony that the compound bar conducted heat 

 according to the calculated amount. 



May 26, 1859. 



Sir BENJAMIN C. BRODIE, Bart., President, in the Chair. 

 The following communications were read : 



I. "On the Intimate Structure, and the Distribution of the Blood- 

 vessels, of the Human Lung." By A.T.H. WATERS, Esq., 

 Lecturer on Anatomy and Physiology, Liverpool. Com- 

 municated by Dr. SHARPEY, Sec. R.S. Received April 7, 

 1859. 



Having been recently engaged in investigating the anatomy of the 

 human lung, I beg to lay before the Royal Society some of the results 

 of my observations with respect to the arrangement of the ultimate 

 air-tubes and the distribution of the blood-vessels of the organ. 



The bronchial-tubes of the lungs, after several divisions and sub- 

 divisions, which for the most part are of a dichotomous nature, 

 terminate in a dilatation, into which open a number of elongated 

 cavities, which constitute the ultimate expressions of the air-tubes. 

 These elongated cavities, to which various names have been given, I 

 propose to call air-sacs, as being, in my opinion, more appropriate to 

 their shape and arrangement than any term hitherto used ; and the 

 series of air-sacs connected with the extremity of each bronchial 

 twig, with its system of blood-vessels, &c., I shall call a lobulette. 



Every lobule of a lung is composed of a number of lobulettes, and 

 thus the description of a single lobulette will suffice for that of the 

 entire lobule. 



Each lobulette consists of a collection of air-sacs, which vary in 

 number from six to eight, ten or twelve. The air-sacs are some- 

 what elongated cavities, communicating with the dilated extremity of 

 a bronchial tube by a circular opening, which is usually smaller than 

 the sac itself, and has sometimes the appearance of a circular hole in 

 a diaphragm, or as if it had been punched out of a membrane which 



