536 APPENDIX.- 



fat, each being composed of numerous distinct and aggre- 

 gated lesser pieces or particles which reflect light strongly, 

 and it is in this circumstance as well as in their large size, 

 that the resemblance borne by these bodies to masses of fat 

 consists. (Plate LXIX. fig. 7.) 



In the natural condition, these bodies are hard and brittle ; 

 after, however, the application of dilute nitric acid, they 

 become soft, the earthy matter being dissolved away, and 

 nothing remaining but their animal constituent ; this, if the 

 acid employed has not been too strong, still retains, to a 

 great extent, the size, form, and appearance of these bodies, 

 previous to its action, and will now readily be seen to exhibit 

 a cellular structure, a cell corresponding to each of the bright 

 constituent pieces above described. If, however, the acid 

 employed be somewhat stronger, these bodies undergo a 

 singular change in form and appearance, the cellated spaces 

 become almost lost to view, and these compound structures 

 assume the characters of large and spherical cells exhibiting 

 numerous concentric lamellae. The earthy matter, then, is 

 contained in these cells or cellated spaces ; the acid dissolves 

 this away, and the entire body becomes so soft, as to admit 

 readily of being torn to pieces with needles ; in this state, its 

 structure may be easily determined, and is seen to consist of 

 membranous elastic tissue. 



These bodies originate in exceedingly small and bright 

 circular discs, which when seen with the quarter inch object 

 glass, are less in size than the head of a pin ; in these appear 

 first, one, and, afterwards, other divisions, indicating the 

 compound and cellular character, which they ultimately more 

 completely exhibit. 



The earthy matter entering into their composition, consists 

 of phosphate of lime, a small portion of phosphate of mag- 

 nesia, and a trace of carbonate of lime. 



Minute sandy particles have been described connected with 

 the choroid plexuses, and that portion of the velum inter- 

 positum which invests the pineal gland ; whether these 

 bodies are of the same nature as those occurring in the gland 



