Royal Sociefj/. 225 



mation of such a nucleus. The deposition ot the phosphates is not 

 followed by that of the other materials. The oxalate of lime is the 

 only substance entering into the composition of urinary calculi, which 

 is ever found in the form of distinct and specific crystallization ; and 

 it then forms what is called the mulberry calculus. The author is 

 led from his observations, to suspect that carbonate of lime, although 

 rarelv found in a separate form in calculi, is not an unfrequent con- 

 comitant of phosphate of lime. With the assistance of Dr. Prout and 

 Mr. Faraday, he ascertained the presence of carbonate of lime in 

 some of the specimens which were not previously supposed to contain 

 it. This result was also confirmed by the analyses of several speci- 

 mens of calculi from the collection in the Hunterian Museum, and 

 also from the Museum of Guy's Hospital, which he was permitted to 

 examine. 



The author is in hopes of being able to make some additions to this 

 communication, if he can obtain permission to divide some of the re- 

 maining calculi in the Norwich collection, so as to give to the Society 

 the result of the whole analysis. 



" On the limits of the pulse in the arteries of the human body," by 

 Lacon Wm. Lamb, M.D. Communicated by Dr. Roget,Sec. R.S. 



The limitation of the pulse to a certain portion of the vascular sy- 

 stem, has been usually ascribed to the dilatation of the arteries con- 

 sequent upon the systole of the heart. If a fluid be injected into an 

 elastic tube, part of the fluid will move forwards in the direction of 

 the canal, while another part will remain to distend the tube, being 

 detained by the various causes of retardation to its passage. If the 

 injection intermit, the detaining force, bearing always a fixed relation 

 to the velocity, will intermit also, and the fluid that remains will 

 now be pressed forwards by the elastic parietes of the tube : it is, 

 however, opposed in its turn by a resistance proportional to its ve- 

 locity, and consequently a permanent tension is maintained through- 

 out the vessel. The fluid which remains during the injection increases 

 with the length of the tube, for the resistance increases with that 

 ratio : hence, the velocity due to the injection must diminish, and 

 that generated during the intermission must increase, as we increase 

 the length of the canal. These velocities tending to equality will ul- 

 timately become equal, provided the tube be of sufficient length, and 

 the result will be an uniform mean velocity. 



The principles now stated are considered by the author as strictly 

 applicable to the circulation of the blood, which receives intermitting 

 impulses from the action of the heart : hence arise inequalities of 

 pressure, and variations of velocity, producing that succession of 

 dilatations of the vessels which is termed jndaation. The author then 

 enters into a mathematical investigation of the length necessary in 

 given vessels to equalize the velocities and the pressures, and endea- 

 vours to show that the point of equality determined from these data, 

 lies within the limits of the arterial system. The calculations are 

 founded on the assumjjtion, tliat in arteries of diflcrent sizes the 

 perpendicular pressure on their walls varies as the area of their sec- 

 3^. S. Vol.5. No. 27. Mrnc/i 1829. 2G tion, 



