CYTOCHEMICAL ASPECTS 



177 



*V 



•hit jr 



\ /f 



/ 



Fig. 4. Distortion of sheath elements during bending of flagellnm. 

 Frozen-dried rat sperm extracted for 10 min in 0.6M KI after glycerina- 

 tion. Stained with PtBr 4 . Longitudinal sections of (a) midpiece and (b) 

 tail. Note reorientation of sheath elements on concave surface of mid- 

 piece compared to those on convex surface; on the convex surface of the 

 tail there is an apparent separation of the sheath elements and a compres- 

 sion of these elements on the concave surface (x 20,000). 



further obviate the necessity for a mechanism to transmit control in- 

 formation to the contractile elements. It would be difficult to recon- 

 cile this argument with the fact that, in rat epididymal sperm, the 

 region anterior to the still unshed kinoplasmic droplet appears 

 quiescent and relatively rigid, while the region distal to the droplet 

 thrashes about actively (Nelson, 1959b). Not only does this observa- 

 tion imply that at least a large proportion of the flagellum, under 

 appropriate conditions, possesses the capacity to participate in local- 

 ized contractile activity, but also that a transmission system inde- 



Fig. 3. Succinic dehydrogenase in frozen-dried rat sperm. Longitudi- 

 nal and transverse sections incubated in (a) polymeric nitro BT tetrazolium 

 and succinate, (b) /?-nitrotetrazolium and succinate, (r) K-tellurite and 

 succinate, (d) veronal buffer and succinate — a control, (e) buffer alone — 

 another control. H, helical sheath; LF, peripheral fibers; MP, middlepiece: 

 T, tail. Note that peripheral fibers are of higher electron density than heli- 

 cal fibrous sheath in tetrazolium- and tellurite-treated specimens, while 

 there is no such density differential in the controls (X 18,000). 



