312 PHILOSOPHICAL TRANSACTIONS. [aNNO IJQS. 



it passes, or as soon as ever it has passed the meridian wire, and read off the mi- 

 croscopes afterwards. Thus every observation is complete ; by ascertaining the 

 right ascension and altitude of every object at once, and with very little trouble ; 

 which must tend greatly to the improvement of our catalogues. 



There is one additional advantage in an instrument of this form ; that we have 

 it in our power to reverse the whole in a few minutes without any hazard ; which 

 I do regularly ; because thus we discover, and destroy, any errors which there 

 may be in the instrument itself, or which may at any time arise in observing. 



XI 1 1. Desciiptio7i of an Extraordinary Production of Human Generation, ivith 

 Observations. By John Clarke, M.D. p. 154. 



In the course of the last year, a woman was admitted into the General Lying- 

 in-Hospital, in Store-street, Tottenham-court-road, who, after a natural labour, 

 was delivered of a healthy child. The birth of this child was succeeded however 

 by a repetition of uterine contractions, by which another substance was expelled, 

 which is the subject of this paper. It was inclosed in a distinct bag of mem- 

 branes, composed of decidua, chorion, and amnios, and had a placenta belong- 

 ing to it ; the side of which was attached to the placenta of the perfect child. 

 The membranes had been opened before Dr. C. saw it, and a small quantity of 

 liquor amnii having been discharged, the contents of the cavity were exposed. 

 The substance contained in the membranes was of an oval figure, rather flattened 

 on the 2 sides. Its long diameter was about 4 inches; and its short diameter, 

 from edge to edge, 3 inches. One edge was rather more concave than the 

 other, and near the centre of it there was a small and thin funis, in length 

 about 1 and \ inch, by means of which it was connected to the placenta. 



The surface of this substance was covered with the common integuments, and 

 from it issued 4 projecting parts. Of these the upper was an imperfect resemblance 

 of the foot of a child, having 1 large and 3 smaller toes on it. The lower was a 

 still more imperfect imitation of a foot, having 1 large and 1 smaller toes. Be- 

 tween the 1 feet was situated a small and rounded projection; into which a small 

 passage led, capable of containing a large bristle, but it soon terminated in a 

 cul de sac. Close to the funis there was another small and thin projection, 

 about 4- of an inch in length, which looked like a finger, and was found to con- 

 tain bony matter, and joints. There was no appearance of head, or neck. No 

 ribs could be felt, nor clavicle, nor scapula. There was no vestige of any thing 

 like legs, or thighs, or upper extremities; or of organs of generation. The 

 only external similarity of this monster to a human foetus, consisted of its cover- 

 ing, and the attempt at a formation of 2 feet, and a finger. 



Before the internal structure was examined, tlie navel-string of the perfect 

 foetus was injected, whence the injection very readily passed through both pla- 



