68 W. .]. DAK IN. 



There is no membrane coverinfj^ the lens and helping' it to 

 retain its shape. Hensen and Hickson could not find such, 

 but Patten described a "suspensory ligament," and also 

 stated that the lens was attached to the septum by a con- 

 nective-tissue ligament (P. varius). None of Patten's 

 successors could find any suspending capsule, neither does 

 the connective-tissue ligament exist. The lens may touch the 

 septum (it very often appears so in sections), but this depends 

 on the contraction during fixation, and usually the retina 

 leaves the posterior wall of the optic vesicle and lies across 

 the middle, coming naturally against the proximal end of the 

 lens. Patten's connective tissue was in all probability the 

 sheath of the distal nerve-branch (Pi. G, fig. 1, Op. Ds-.), 

 which would be touching the lens and lying between this and 

 the septum if the retina had been forced up. Patten's 

 theories of accommodation as expressed at some length on 

 p. 571 I cannot confirm, and they are somewhat irrational. 

 They have not been referred to at all by his successors. He 

 believed that the contraction of certain muscles supposed to 

 be attached to the suspensory ligament would cause a move- 

 ment of the lens towards the retina. This meant an inward 

 movement of the septal membrane to which the lens (accord- 

 ing- to Patten) was attached. The elevation of the lens was 

 to be brought about " by the tendency of the elastic septal 

 membrane to return to its natural position, after the contrac- 

 tion of its peripheral circular fibres has relaxed the tension 

 upon the central portion." 



There is, however, no suspensory ligament nor attached 

 muscles, and the lens is not attached to the septum. The 

 septum, moreover, cannot move forward without taking the 

 whole of the retina with it, and if this was the case (rather an 

 absurdity) the recipient elements would always be the same 

 distance behind the lens, whether it had been elevated or 

 otherwise. Accommodation will be referred to later when 

 discussins* Hesse's theorv. 



The lens cells had received little attention until Hesse 

 described them (34). Hensen stated that the lens consisted 



