Transactions of the Royal Society, 335 



feature to the history of these extraordinary animals, which is, that 

 the Planaria Cornata sometimes obtains an additional head, in 

 consequence of injury or artificial incision. Dr. J. took about a 

 hundred Planarice Cornutce, and made in each an incision on the 

 side of the body ; in one instance only, the desired result was ob» 

 tained, and after about a fortnight, a perfect head had grown out 

 of the wound, producing a double-headed Planaria. In the greater 

 number of cases, the incisions healed, or only produced wens and 

 other irregularities. 



iii. On the Influence of Nerves and Ganglions in producing Animal 

 Heat. By Sir E. Home, Bart. V.P.R.S. Communicated by the 

 Society for the Improvement of Animal Chemistry. 



In the most simple animal structures endowed with life, large 

 enough to admit of dissection, brain and nerves are met with, 

 although many such animals possess 'no power of preserving a 

 temperature higher than that of the atmosphere by which they 

 are immediately surrounded. This is the case with the oyster, 

 the fresh- water mussel, and the garden- snail : they have a brain 

 and spinal marrow, but no ganglions. 



In the leech, the earth-worm, and all the insect tribe, the 

 brain and spinal marrow very closely resemble that of the garden 

 snail ; but in all these tribes there is a pair of nerves running 

 down from the spinal marrow the whole length of the body of the 

 animal, which are united together at regular intervals by what 

 are called ganglions, composed of nervous fibres, apparently en- 

 tangled and agglutinated together ; and in all such animals it 

 was proved by Mr. Hunter, in his paper on heat, that their tem- 

 perature exceeds that of the atmosphere when below 56°, although 

 in very different proportions ; the excess in the leech being only 

 one degree, while in a hive of bees it is 26°. 



As the only difference between the nervous systems of those 

 animals that have no power of producing heat, and those that have, 

 consists in there being ganglions, Sir Everard was led to suspect 

 that this power was derived from the ganglions with which the 

 nerves are furnished. 



" To ascertain how far there were sufficient grounds for this 

 suspicion, I began to consider, whether any parts of animals pos* 

 sessed of an unusual temperature were devoid of nerves ; the heat 

 of the deer's horn while enclosed in its velvet, in June, 1824, when 

 only one foot long, I found to be 96°, and on the 12th of July the 

 tip of an antler was 99 £ ; from which it was evident that these 

 horns, during their growth, have a power of producing heat, inde- 

 pendent of the direct influence of the brain or heart ; and there- 

 fore it was only necessary to ascertain whether there are nerves 

 accompanyiug their blood-vessels, which Mr, Bauer not only ascer- 



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