Ch. XI] 



SERIAL MICROSCOPIC SECTIONS 



407 



bottom of the box (§ 612); and arrange the object exactly over the 

 orientation diagram in the bottom of the imbedding box (§657). 



(2) Mount the block of paraffin containing the embryo so that 

 the caudal end is next the microtome holder. The head is then cut 

 first, and the caudal surface of the sections will rest upon the slide, 

 bringing the cephalic face up (fig. 238). 



(3) Place in the microtome so that the right side of the embryo 

 or animal meets the edge of the knife. 



(4) Mount the sections like the "words in a printed line. This will 

 bring the first or most cephalic section at the upper left-hand corner. 



Homo 



_3 



40 



Homo 3 

 Si 40 



Sec 493 



20 H 504 



1900 



Fig. 239. A Slide of Serial Transections Showing the Arrangement and 



the Labeling of the Slide. 



The cephalic face will be up, and the dorsal aspect next the upper 

 edge of the slide. 



Under the compound microscope the rights and lefts will appear 

 as in the observer's own body, as will also the dorsal and ventral 

 parts. 



Frontal Sections 



§ 663. Frontal sections. — These are sections made by dividing 

 the body into equal or unequal dorsal and ventral parts. 



(1) Imbed the animal or embryo with the right side down in the 

 imbedding mass (§ 612) ; and arrange the object exactly over the 

 orientation diagram in the bottom of the imbedding box (§657). 



(2) Mount the block of paraffin containing the embryo so that 

 the ventral aspect of the embryo or animal is next the disc of the 

 microtome holder (fig. 240). The dorsal part is then cut first, and 

 the ventral surface of the sections will rest upon the slide, bringing 

 the dorsal face up. 



