520 SUMMARY OF CURRENT RESEARCHES RELATING TO 
remain very ignorant on the subject, the author shows at least that the 
term is made to include substances which are certainly not identical. 
Tho pigment in the epidermis and hair of mammals, in the frog’s 
skin, and in naevi and melanosarcomata, is indifferent to concentrated 
hydrochloric acid ; it is dissolved but not changed by boiling ; it dis- 
appears in nitric acid ; but is unchanged in sulphuric acid, caustic potash, 
&c., even when heated ; it is not dissolved or changed by water, alcohol, 
chloroform, &c. If an indubitable hmmatogenic pigment, e.g. that of 
sarcomatosis cutis, be subjected to similar tests, the results are altogether 
different. The pigment of plasmodium malarias is also different from 
any hitherto investigated melanotic pigment of Vertebrates ; and the 
black pigment of Crustacea, &c., agrees rather with that of the plasmo- 
dium than with that of Vertebrates. 
By a study of skin-sections, Rosenstadt has convinced himself that 
epidermic cells, like connective-tissue cells, are able to form pigment 
independently. This was corroborated by an investigation of chick 
embryos, and of the retina cells in Lucifer regnaudii , &c. He goes 
on to discuss the various modes in which the pigment occurs in the 
skin, — in pigment-cells beneath the epidermis (Invertebrates) ; in me- 
lanoblasts occurring as fixed connective-tissue-cells in the cutis, and 
partially giving off pigment to the epidermis-cells (lower Vertebrates) ; 
in the epidermic cells themselves with or without the simultaneous 
occurrence of pigment-cells in the cutis (Mammals). 
Periostal Ossification.* — Dr. G. Kapsammer discusses the much- 
debated question as to the relation between periostal and endochondral 
ossification. Making an exception for the epiphyses and partially for 
the vertebrae, he sums up the results of his studies in the following 
conclusions : — 
(1) The periostal ossification appears before the endochondral ; 
(2) Periostal ossification consists in the metaplasis of a connective 
tissue rich in cells ; 
(3) The skeletal system of the adult is in greater part formed in 
a periostal manner ; 
(4) Endochondral ossification has for the most part a provisional 
character. 
Dorsal Cells of Spinal Medulla.f — Prof. A. Van Gehuchten dis- 
cusses the occurrence of the peculiar elements known as dorsal cells 
or Hinterzellen in various Vertebrates. In Cyclostomes they persist 
throughout life, and are in connection with the posterior roots ; they 
may be considered as homologues of the cells of the spinal ganglia. 
In flat-fishes the dorsal cells persist throughout life (Dahlgren), but 
the course of their axis-cylinder processes is not known. In Baja , 
Acipenser , Lepidosteus, Salmo , Trutta, BJiodeus, Labrax , the dorsal cells 
occur in the embryo, and are in connection with the posterior roots ; 
but their subsequent history is uncertain. 
What the author particularly emphasises is that this term “ dorsal 
cells ” is at present applied to two quite different groups of nerve- 
elements. (1) There are the cells of Kutschin-Freud or of Reissner- 
* Arch. Mikr. Anat., 1. (1897) pp. 315-50 (1 pi.), 
t Bull. Acad. Roy. Belg., xxxiv. (1897) pp. 24-38.' 
