411 



contrary, lie supposes that though its velocity is less than m summer, 

 it still bears a considerable proportion to it. . 



Monday, 6t/i March, 1843. 

 The Right Honourable Lord GREENOCK, Vice-President, 



in the Chair. 

 The following communications were read : — 



1. On the Nature, Locality, and Optical Phenomena of Muscae 



Volitantes. By Sir D. Brewster, K.H. 



2. On the Structure of the Lymphatic Glands. By John 



Goodsir, Esq., Conservator of the Museum of the Royal 

 College of Surgeons of Edinburgh. 



The author stated that the different lymphatics, as they enter the 

 gland, become deprived of their external tunic, which passes on to 

 the surface of the organ, to assist in forming its capsule. The 

 middle tunic also becomes weaker, and presents the appearance 

 of fibres arranged in the form of arches, which enclose rounded 

 or oval spaces, particularly towards the surface of the gland, 

 and at the angles formed by the anastomosis of one lymphatic 

 with another. Mr Goodsir then observed that it was to the 

 changes which the internal tunic of the lymphatics undergoes in the 

 interior of the gland, that these organs owe their peculiar structure. 

 This tunic, when traced from the afferent or efferent vessels into the 

 gland, is found to become thicker and more opaque, till at length it 

 no longer transmits light. It consists of two parts — a fine external 

 membrane, and a granular substance attached to the inner surface of 

 that membrane. The membrane belongs, according to the author, 

 to the class of germinal membranes, with the germinal spots placed 

 at regular distances. This germinal or primitive membrane of the 

 internal tunic of the intra-glandular lymphatics is extremely delicate, 

 and has germinal spots of an oval form, with compound nuclei. 

 These spots are the sources of the nucleated particles which come 

 from the granular substance. These particles arc about the 4000th 

 to the 5000th of an inch in diameter, and form a considerable propor- 

 tion of the corpuscles, which have been long recognised in the fluid 

 which may be squeezed out of lymphatic glands. The layer 

 which these nucleated particles forms on the internal surface of the 

 germinal membrane is so thick as almost to fill the cavity of the 

 lymphatic. The canal of the vessel is irregularly pierced through 

 the granular substance, the surface and particles of which are freely 



