MECHANfSM OF LBAF-STALKS. 



179 



in the thoracic dnct. This fact I ascertained at the Veteri- 

 nary College, assisted by the deputy professor Mr. Sewell, 

 and Mr. Clift. These lymphatic vessels are equally large conveying iu 

 as the excretory ducts of any other glands, and therefore suf- secretion into 

 ficient to carry off the secretion formed in the cells of the ,juct. **""* 

 spleen ; and where a secretion is to be carried into the tho- 

 racic duct, it would be a deviation from the general plan of 

 the animal economy, were any but lymphatic vessels em- 

 ployed for this purpose. 



It is a strong circumstance in favour of the secretion be- 

 ing so conveyed, that in the last experiment, the lacteals and 

 cells of the spleen were unusually turgid, being placed un* 

 der similar circumstances, the thoracic duct being so full as 

 not to receive their contents. 



The purposes that are answered by such a secretion from 

 the spleen into the thoracic duct cannot at present be ascer- 

 tained* 



IV. 



0/ the mechanical Powers in the Leaf Stalks of various Plants, 

 Inm Letter from Mrs. Agnes Ibbetson. 



To Mr. NICHOLSON. 

 SIR, 



AN pointing out what appears to me to be the perfection Mechanical 

 of mechanism in the hairs of plants I have by no means ex- pi^^jj."* 

 hausted the subject, but rather begun it. The mechanism 

 of botany, though not yet familiarized to our ideas, is not 

 the less beautiful, or true. As I have introduced it, so 1 

 shall continue to exhibit specimens of it, showing, that 

 there is not a part of a flower, leaf, or stem, that is not ma- 

 naged by mechanical means. This is admirably depicted depicted in th« 

 in the leaf stalk, which I shall make the subject of the leaf-^ta'^s- 

 present letter ; as Mr. Knight, in his view of it, has given 

 only one sort of peduncle^ without deacribiog the increased 

 N « size 



