328 JAMES EDWARD ACKERT 



very complex. The general structure of these pericellular plex- 

 uses, the absence of definite observations upon endings of sym- 

 pathetic neurites (post-ganglionic) on sweat glands, and the strik- 

 ing hoop-like arrangement of these fibrillar stripes around the 

 glands, lead the writer to question whether, perhaps, the post- 

 gangUonic neurites may not form simple plexuses about the glands 

 more or less similar to the pericellular plexuses about the cell 

 bodies of the sympathetic neurones. Such an arrangement of 

 the terminal fibers of a post-ganglionic neurite would be most 

 effective. The nerve threads lying immediately upon the smooth 

 muscle fibers and the bases of the gland cells could form functional 

 connections with them. This view of the endings of post-gangli- 

 onic neurites on modified sweat glands seems somewhat more 

 plausible from the fact that these circular fibrillar structures appear 

 about the glands only in their secretory portions, and likewise 

 only in the regions covered by the longitudinal smooth muscle 

 fibers. 



WHAT SENSORY ORGANS ARE CONCERNED WHEN BLINDED BATS 

 AVOID OBSTACLES WHILE ON THE WING? 



Although the present problem is primarily a morphological one, 

 yet a discussion of the function of the integumentary sensory 

 structures described may not be out of place here. Of especial 

 interest is the question of the means by which blinded bats avoid 

 obstacles while on the wing. A number of investigators, experi- 

 menting with living bats, have maintained that the organ con- 

 cerned in these delicate reactions is the skin. A brief summary 

 of their opinions follows. 



As already noted, Cuvier thought the fljdng bat, on approach- 

 ing an object, sets up air currents, which react on the patagium, 

 enabling the animal to avoid the obstacle. 



Jobert ( 72) observed that on pinching the skin, the animals re- 

 sponded faintly as compared with their vigorous reactions when 

 hairs were pulled out. This led him to think that the sensitive- 

 ness of the flying membrane is due to the hairs. He inferred that 

 currents of air affect the hairs and that each movement of the lat- 



