ZOOLOGY AND BOTANY, MICROSCOPY, ETC, 41 



Chicken Bone-marrow in Plasma Medium.* — Rhoda Erdmann 

 describes a first period (first to third day) of a somewhat regressive 

 character — inchiding the degeneration of the erythrocytes and the 

 nearly full-grown erythroblasts, the ripening of the granulocytes im- 

 planted with the bone-marrow into the tissue culture, the decay of the 

 bone-marrow into a network. In the second period (third day to death 

 of culture) there is an adaptation of surviving cells to the conditions of 

 the medium. The surviving cells are modified fat cells and newly 

 formed wanderins- celia of the mesenchyme-like type. After fourteen 

 days' cultivation, they are, except elongated connective tissue cells, the 

 only living cells. They belong to the conneciive tissue cell type, and 

 may, when the medium is renewed, grow indefinitely. 



Osseous Regeneration in the Adult. f — Heitz-Boyer and Scheike- 

 vitsch maintain that ossification in adult man, effecting regeneration, is 

 always a pathological process, inflammatory from beginning to end. It 

 is not a re-awakening of the latent powers of the periosteum. The 

 primum movens of the ossification of the periosteum in an adult is 

 always accidental, and originates in a bone afl'ected by osteitis. The 

 periosteum offers an eminently favourable soil, but it has no generative 

 action. This belongs exclusively to the bone. 



Epithelial Reversions in Human Thymus, ij: — A. P. Dustin has 

 studied the intrathymic epithelial formations which occur in varying 

 degrees in the thymus. They are due to reversionary involution of the 

 primary cells of the thymus. They may last a long time, but they do 

 not give rise to any other structure. 



Structure of Optic Nerve. §— Nicola Alberta Barbieri describes the 

 optic nerve in various types. In fishes it has two forms, cylindrical and 

 laminar. In Gadidse, Muranidte, and cartiUiginous fishes it is cylin- 

 drical ; in the others it is laminar. A deep groove (also seen in 

 Ruminants) marks the end of the cyliudrical optic nerve ; it is absent in 

 the laminar optic nerve. In Labrax lupus the optic nerves form a 

 plaited membrane. In birds the optic nerve is laminar in diurnal birds 

 of prey and web-footed birds ; it is cylindrical in nocturnal birds of 

 prey and other birds. Barbieri contrasts the Vertebrate optic nerve with 

 what occurs in Cephalopods, where very short optic nerves lead into 

 large optic ganglia, surrounded by a capsule, and are not continued into 

 the retina. 



Intercalated Discs in Heart-muscle of Ox.|| — H. E. Jordan and 

 J. B. Banks have made a careful study of the intercalated discs in 

 heart-muscle, which have been interpreted as (1) intercellular cement 

 substance ; (2) regions of muscle-growth or differentiating sarcomeres ; 



« 



Amer. Journ. Anat.,xxii. (1917) pp. 73-126 (9 pis. and 2 flgs.). 

 t Comptes Rendu?, clxv. (1917) pp. 518-20. 



J Arch. Zool. Exp^r., Ivi. (1917) Notes et Revue, No. 4, pp. 73-87 (7 figs.). 

 § Comptes Rendus, clxv. (1917) pp. 677-80. 

 Jl Amer. Journ. Anat., xxii. (1917) pp. 285-339 (4 pis.). 



