The Influence of Water and Light and the Pituitary Upon the Pigmentary System of the Common Toad (Bufo Bufo Bufo)

1. Bufo bufo bufo shows no melanophore response to moisture. 2. The severance of the optic nerve or the removal of the eyes causes a cessation of secondary responses to illuminated background. Some melanophore activity remains. 3. The cauterization of the optic chiasma or the infundibular stalk brings about the permanent expansion of the melanophores. 4. Hypophysectomy, and cauterization with hypophysectomy, both produce permanent contraction of the melanophores. 5. The implications of these results in relation to chromatic control are discussed.

XVIII. On the powers on which the functions of life the more perfect animals depend, and on the manner in which they are associated the production of their more complicated results

In considering the powers of life, I shall in the first place inquire into the seat, the functions and the nature of each of these powers; and then point out the manner in which they are associated in the production of their more complicated results. Of the powers of the living animal the simplest is that by which the motion of its various members is effected, and which essentially contributes to all its more complicated functions, the contractile power of the muscular fibre, the healthy action of which is not a state of uniform contraction but of a constant and generally rapid succession of contractions and relaxations. Its permanent contraction we have reason to believe is always a state of disease.