250 THE RETINA, BY MAX SCHULTZE. 



which have become serrated, are not caused by a process of 

 shrinking. The form of the natural transverse section of the 



o 



outer segment in the fresh state is exactly the same. I have 

 shown that the longitudinal striation, which is more easily seen 

 in Amphibia and Fishes on account of the larger size of the 

 outer segments, is also present in Man and Mammals, and here 

 also probably depends upon a channelling of the surface. It is 

 a highly remarkable circumstance that the transverse section 



Fig. 354. 



ooO o 



QCPQ 



Fig. 354. a, External segment of a Triton examined in the fresh 

 condition in serum ; b, thin disk of the same, broken off after treat- 

 ment with a two-per-cent. solution of perosmic acid, seen some- 

 what laterally. The remaining figures represent similar or even still 

 thinner disks, seen from the surface, with fissures penetrating to a 

 variable depth. Magnified 1,000 diameters. 



of the large external segments of Amphibia (Triton) and Fish 

 (Syngnathus) often differs considerably from the circular form, 

 and may present an irregular dentated border, or even be of 

 semilunar shape. 



Several observers have expressed themselves in favour of 

 the existence of an axis fibre running in the interior of the 

 external segment. Hitter's* first description, as well as the 

 corroborating observations of Manz and Scliiess,")* lead to the 

 supposition that we are here 'dealing with appearances that 

 owe their origin to the action of the preserving fluids ; but if in 

 a perfectly fresh Mammalian retina we obtain a surface view of 



* Grafe's Archiv fur Ophtlialmologie, Band v., Abtheil ii., p. 101, 

 Taf. iv. 



t Zeitschrift fur rationelle Median, Band x., p. 305. 1860. 

 J Idem, Band xviii., p. 128. 1863. 



