234 
<®bi.gittnl Jtrfirlfig. 
XX.—IIeineich Rathke.—On the Development oe the Ceanitjm 
IN THE YeETEBEATA. 
[The active and long continued labours of the head and founder, after Van Baer, of 
that modem science of Embryology which is the necessary precursor of ah 
philosophical anatomy worthy of the name, are now unfortunately ended, 
Professor Rathke having died suddenly and unexpectedly while presiding over 
the Scientific Congress which met in Konigsberg three years ago. So long as the 
venerated master lived, it behoved those who had learned so much from him 
respecting the development of the vertebrate skull to wait for the fulfilment of 
the promise half given in the opening paragraphs of the masterly essay here 
translated. But there is no sign that any larger work on this subject remains 
among the papers of the deceased philosopher, and therefore, the translator, 
imagining that others may find it as difficult as he has done to procure the 
original “ Vierter Bericht uber das naturwissenschaftliche Seminar bei der 
Universitat zu Konigsberg—nebst einer Abhandlung uber die Entwickelung 
des Schadels der Wirbelthiere,” published at Konigsberg thirty-four years ago, 
(1839) offers this version of a memoir which is at this moment the best and 
most comprehensive account of the development of the skull extant. Hereafter 
the translator will take occasion to point out how far later inquiries by Rathke, 
or by others, may necessitate the modification of some of the paragraphs of this 
essay.—T. H. H.] 
§ 1. While occupied during the last few years, with investiga¬ 
tions into the development of the Snake, I was much surprised at 
the mode in which the formation of the skull commenced—and I was 
thus induced to examine the same process in other vertebrata; 
the more especially as I entertained the hope that the study of its 
development would tend to elucidate the view that the skull is com¬ 
posed of several modified vertebrae. 
But in putting forth the results of the observations bearing on 
this question, which I have made, it must be remembered that they 
are but the outlines of a work, which I propose to complete by 
further researches. 
§ 2. If any trustworthy result is to be attained from attempts to 
explain the skull as consisting of several modified vertebrae, they 
must be based on an acquaintance with the development of the spinal 
column. Therefore I shall premise an account of the most essential 
steps in the development of that part. 
§ 3. That which constitutes the foundation of the spinal column, is 
the notochord, a membranous tube, closed on all sides and filled with a 
gelatinous substance. Hence the notochord consists, in and for 
itself, of two different parts which may be termed the axial substance 
and the sheath. Bound it is deposited a blastema, which at first, has the 
same coarsely granular composition throughout. It seems to make 
its appearance first on the right and left sides of the notochord, and 
then gradually to grow above and below round the notochord, so that 
after a certain time, the latter is coated with it, as by a new or second 
