99 



tact with tlie scalp of a child, whose head is not well cared for, attach 

 themselves to the epithelium, or find a lurking-place in the hair 

 follicles. There they rapidly reproduce themselves, distend the hair 

 sacs, press upon the roots of the hair, and finally, entering into its 

 substance, produce a discoloration and brittleness, which causes it to 

 break off at a short distance above the surface of the scalp. This 

 process repeats itself indefinitely if unchecked, causing general bald- 

 ness, and large unsightly formations of a bad odor. The plant may 

 also grow upon the skin of other parts of the body ; but there, failing 

 to find a lodging-place so secure as the hair follicles of the head, is 

 easily removed, and never forms crusts of any considerable size. 

 When seated on the scalp, it can only be cured by pulling out all the 

 aifected hairs. Its infectious nature may be proved by transplanting 

 it from one person to another. It is, fortunately, a disease of rare 

 occurrence, less frequently seen than the other vegeto-parasitic dis- 

 eases of the scalp. Whether the disease belongs naturally to the 

 mouse or to man, we have no means of determining ; he believed it 

 had never been observed upon any other animals than the mouse 

 and cat. 



Prof. Silliman inquired if any of the members had heard 

 of the arrival in Boston of a large quantity of the maguesian 

 mineral Rhodizite, a cargo of which is said to have been 

 shipped from Africa. It is a rare substance, heretofore 

 found only in Siberia, and if occurring in abundance, as is 

 alleged, in Africa, will be of considerable commercial impor- 

 tance from the boracic acid it contains. 



The Corresponding Secretary read the following letters 

 recently received, viz : 



From the Academie des Sciences de Lynn^ June 11, 1860, sending 

 its Memoires; from the Academie des Sciences de Russie, June 27, 

 acknowledging the receipt of the Society's proceedings ; from the 

 Vereinfiir vaterldndisclie Naturkunde in Wiirttemherg, Stuttgart, Sept. 

 1 , acknowledging the receipt of the Society's pubhcations and sending 

 their own ; from the Royal Institution, London, Sept. 28, acknowledg- 

 ing the receipt of the Proceedings ; from the K. AJcademie der Wis- 

 senschaften, Wien, Oct. 10, sending their Proceedings and asking for 

 wanting numbers of the Proceedings of this Society ; from the Micro- 

 scopical Society, London, Nov. 15, acknowledging the receipt of the 

 Society's pubhcations and a box of shdes of microscopic objects ; 

 from Mr. H. Davis, of McGregor, Iowa, Dec. 8, asking for an ex- 

 change of Mississippi River for marine shells. 



Dr. S. Weir Mitchell, of Philadelphia, was chosen Corre- 

 sponding Member, 



