86 W. J. DAKIN. 



it is a semi-fluid substance of connective-tissue-like nature, 

 which contains some oil or fatty body, and I have called it 

 the rod-matrix (PL 7, Hg. 17, li. mat.). 



Patten described the rods, which are very difficult to 

 preserve, as consisting of a " liyaline refractive sheath 

 surrounding a pyramidal axial core filled with a watery non- 

 refractive fluid, and a short distance from tlie inner ends of 

 the rods, terminating in a rounded apex" ([22], p. 585). 

 This axial core is, in my opinion, the true rod, and what he 

 described as the sheath is the surroundiug rod-matrix. 

 Carriere (21), had noticed this before Patten, and described 

 the rods as being immersed in a fatty substance. Patten, 

 however, adds that this was due to the fusion of the sheaths 

 of the poorly preserved rods. Rawitz agreed with Patten 

 about this sheath, though he differed slightly in regard to 

 its optical properties, and Scbreiner also does not accept 

 Carriere's view. Hesse's view is, however, the same as mine, 

 and he has emphasised ihe error of Patten, Pawitz, and 

 Schreiner, whose peculiar idea of the rod was due to the fact 

 that they believed an outer sheath to be necessary. The rod 

 structure differs from that of tlie rod-cell in the fact that 

 there is much less stainable protoplasm, and this is usually 

 aggregated round an axial fibre (PI. 7, tig. 13, Ax./.). It 

 will be unnecessary here to go into further comparisons of 

 the previous views on these structures. The rod-cells have 

 been described almost correctly, though with deficiencies by 

 most observers, with the great exception of Hyde, whose 

 account I am leaving until later. 



In sections of well-preserved rod-cells and rods, such as 

 those fixed in Bouiu or Zenker and stained in Mallory's stain, 

 an axial fibril will be easily seen rtinning through the rod. 

 It is wiih reference to this structure that most of the con- 

 fusion has arisen. Patten stated that each rod-cell contained 

 an axial nerve-fibre which entered the attenuated end, passed 

 through the first vesicle-like swelling, passed the large 

 nucleus, and went on down to the lower end of the rod, 

 whence it issued, and divided into two main branches which 



