384 PRACTICAL HISTOLOGY. [XXXV. 



sections in hsematoxylin or picro-carmine, and mount in balsam. 

 The hardened testis of a small animal, e.g., rat, should also be 

 st'ained in bulk in borax-carmine or Kleinenberg's logwood, and cut 

 in paraffin, so as to include the body of the testis and the epididymis. 

 Mount in balsam. 



(ii.) Harden very small pieces of the testis of a freshly-killed 

 rat or mouse in Flemming's mixture and stain the sections in 

 safranin. A very small testis is taken, as Flemming's fluid only 

 penetrates a few mm. into the tissue. This is for the study of 

 spermatogenesis. 



(iii.) Harden the testis of a frog in absolute alcohol and stain 

 it in bulk in Kleinenberg's logwood. 



(iv.) Harden the testis of the dogfish in Flemming's fluid and 

 stain the sections in hsematoxylin or safranin. This, as shown by 

 Swaen, is an excellent object for the study of spermatogenesis. 



(v.) Harden the testis of a mouse, salamander, or frog in the 

 following fluid 1 in which platinic chloride is substituted for the 

 chromic acid in Flemming's chromo-aceto-osmic acid mixture : 



Hermann's Fluid, 



Platinic chloride (i per cent.) , 15 parts. 



Osmic acid (2 per cent. ) . . 4 ,, 



Glacial acetic acid I part. 



The above is used for the tissues of mammals ; but if a salamander 

 testis is used, then take only 2 parts of the osmic acid. 



After 2-3 days the details of the cells are better brought out 

 than with Flemming's solution. Complete the hardening in alcohol. 

 Make sections in paraffin, fix them on a slide with albumin fixative, 

 and stain for 24-48 hours in the following safranin fluid : 



Safranin I gram. 



Alcohol . . . 10 cc. 



Water . , , 90 ,, 



After staining, wash in water, acid-alcohol and alcohol, but do 

 not remove all the surplus safranin. Then stain for 3-5 minutes 

 in a gentian-violet solution. Decolorise the sections by means of 

 Gram's method (p. 105), i.e., after washing in alcohol, place them 

 for 13 hours in the following fluid 



Iodine I gram. 



Potassic iodide . . .2 grams. 



W uter .... 300 cc. 



until they are quite black, and then differentiate them in alcohol. 

 Mount in balsam. 



1. T.S. Testis (Rat}. (a.} Observe the thick, tough, fibrous 

 tunica albuginea with sections of large blood-vessels and lymphatics 



1 Archiv f. mik. Anat., xxxiv. p. 58. 



