272 Dr. Waller on some Tissues of the Animal Frame, 



strongest magnifying powers we possess. It is inserted by the 

 base to the concavity of the lower jaw-bone, and the point hangs 

 down the pharynx perfectly free from any adherence. It pre- 

 sents great resemblance to the uvula in the human subject in 

 size, shape and colour, which also has its lower extremity free 

 and hanging down the pharynx. The peculiar habits of the 

 frog completely explain the apparently anomalous disposition 

 of the tongue ; as, independently of its being an organ of taste, 

 it likewise serves the purpose of one of prehension for sup- 

 plying the animal with food. As is well known to naturalists, 

 it subsists on flies and small insects which it seizes in their 

 flight. On these occasions it darts its head forward, at the 

 same time projecting the tongue out of the mouth, the upper 

 surface of which being covered with a slimy exudation, comes 

 in contact with the insect, folds round it and draws it back 

 into the mouth. In this little manoeuvre the tongue may be 

 considered as performing a movement of rotation of 180° 

 round the lower jaw-bone, so that the surface which is upper- 

 most in the mouth becomes lowermost when in contact with 

 the object. This fact must be borne in mind when the tongue 

 is examined under the microscope, for then likewise the in- 

 ferior surface is uppermost, and the superior or papillary sur- 

 face below. 



I take this opportunity of staling my claim of priority with 

 regard to this experiment, as a very erroneous impression 

 might be created by M. Donne's statement in his Corns de 

 Microscopic It was first performed by ine in Paris in 1839. 

 The idea occurred to me while making some dissections of the 

 frog for the purpose of comparative anatomy; and at first I 

 merely applied it to test M.Dumas's well-known theory of mus- 

 cular contraction. Subsequently I repeated it in the presence 

 of several of my friends, among whom I may particularly men- 

 tion Mr. Thomas Cooper. Success in this point encouraged 

 me to attempt to observe the circulation in the human subject; 

 and as the prepuce in some cases is nearly semi-transparent, 

 I fixed upon that membrane as the subject of experiment. 

 For an obvious reason I was desirous of not making these 

 experiments alone, and obtained the assistance of M. Donne. 

 After a few attempts we finally abandoned the subject; 

 although I am still of opinion that they would be successful if 

 tried under favourable circumstances. While engaged in this 

 pursuit I stated to him that I had already discovered a living 

 membrane, containing muscles and glands in its natural state, 

 without the aid of the scalpel. From the interest with which 

 I found this observation received by him, I was induced to 

 repeat the experiment as described, and we determined to 



