*44 



Microscopical Essays. 



Some fubflances are, however, fo organized, that if their pecu- 

 liar form is altered, the parts we with to difcover are deftroyed ; 

 •fuch as nerves, tendons, mufcular fibres, pith of wood, &c. 

 many of thefe are beft to be examined while floating in fome con- 

 venient tranfparent fluid. For inftance, very few of the fibres of 

 any of the mufcles can be difcovered when they are viewed in 

 the open air ; but if placed in water or oil, great part of their 

 wonderful fabric may be difcovered. If the thread of a ligament 

 is viewed in this manner, it will be feen to confift of an indefinite 

 number of fmooth round threads lying clofe together. 



Objects of an elaftic nature fhould be pulled or flretched out 

 while they are under the microfcope, that the texture and nature 

 of thofe parts, whofe figure is altered by being thus pulled out, 

 may be more fully difcovered. 



To examine bones with the microfcope. Thefe fhould firfr. 

 be viewed as opake objects; afterwards, by procuring thin 

 feclions, they fhould be looked at as if tranfparent. The fections 

 fhould be cut in all directions, and be well wafhed and cleaned ; 

 a degree of maceration will be ufeful in fome cafes. Or the 

 bones may be put in a clear fire till they are red hot, and then 

 taken out; by this means the bony cells will appear more con- 

 fpicuous and vifible, being freed from extraneous matter. 



To examine the pores of the skin. Firft, cut or pare off 

 with a razor as thin a flice as pofhble of the upper fkin ; then cut 

 a fecond from the fame place ; apply the laft to the microfcope. 



The 



