The dioptric arrangement, being the reverse of that which obtains in animals where "accommodation" is observed, and in whom the passive state is that of vision, arranged for distant objects, while the active state is that of vision accommodated at will for near objects.
4th. That the vascular distribution of the choroid vessels has no relation to any movement of the lens or change of its shape, but is arranged to meet the changes of static condition of the circulating fluid, and of dynamic force exerted by the heart under varying pressure from without; and that by such an arrangement, protection to the delicate tissues of the eye is afforded by a compensating balance between the tension of the blood within the vessels and the external pressure exerted upon them.
[17] "Lieutenant and Commander," by Captain Basil Hall. Bell & Daldy, London.
Transcriber notes:
[P.24.] 'he Equator.' changed to 'the Equator'.
[P.81.] 'Marseileise' changed to 'Marseillaise'.
[P.161.] Fig. 75. 'Dendrophylia' changed to 'Dendrophyllia'.
[P.186.] 'd'Acclimitation' changed to 'd'Acclimatation'.
[P.203.] Fig. 87. 'Hydra viridris' changed to 'Hydra viridis'.
[P.224.] 'vetebrated' changed to 'vertebrated'.
[P.299.] 'duvernea' changed to 'duvernæa', also in the list of illustrations.
[P.318.] 'coattings' changed to 'coatings'.
[P.335.] 'themeslves' changed to 'themselves'.
[P.352.] 'Malægrina' changed to 'Maleagrina'.
[P.403.] 'insensi le' changed to 'insensible'.
[P.408.] 'connnection' changed to 'connection'.
[P.426.] Plate XXIII. Fig. III. 'Vlouta' changed to 'Voluta'.
[P.523.] 'other other' changed to 'other'.
[P.531.] 'it own' changed to 'its own".
[P.580.] Added 'Plate' to illustration XXIX, 'Plate XXIX.'
[P.581.] 'cranes' changed to 'crans'.
Fixed various punctuation.