36 Dr. Beale on a New Object-glass. [Jan. 19, 



by Messrs. Chance, of Birmingham, or mica, and there is plenty of room 

 for focusing to the lower surface of thin specimens, which can alone be 

 examined by high powers as transparent objects. I beg to draw attention 

 to these very high powers at this time more particularly, because the facts 

 recently urged in favour of the doctrine of spontaneous generation lately 

 revived may be studied with great advantage. Not only are particles, too 

 small to be discerned by a sixteenth, well seen by a twenty-fifth or a 

 fiftieth, but particles too transparent to be observed by the twenty-fifth 

 are distinctly demonstrated by the fiftieth. I feel sure that the further 

 careful study, by the aid of these high powers, of the development and 

 increase of some of the lowest organisms, and the movements which have 

 been seen to occur in connexion with certain forms of living matter (Amoeba, 

 white blood-corpuscle, young epithelial cells, &c.), will lead to most va- 

 luable results bearing upon the much debated question of vital actions. 



Another very great advantage resulting from the use of the highest 

 powers occurs in minute investigations upon delicate structures which 

 occupy different planes, as is the case in many nervous organs. In study- 

 ing the distribution of the nerves in some of the peripheral organs of 

 vertebrate animals, very fine fibres can be followed as they lie upon dif- 

 ferent planes. 



The most delicate constituent nerve-fibres of the plexus in the summit 

 of the papillae of the frog's tongue (New Observations upon the Minute 

 Anatomy of the Papillae of the Frog's Tongue, Phil. Trans, for 1864), 

 can be readily traced by the aid of this power. The finest nerve-fibres 

 thus rendered visible are so thin, that in a drawing they would be repre- 

 sented by fine single lines. Near the summit of the papilla there is a 

 very intricate interlacement of nerve-fibres, which, although scarcely brought 

 out by the twenty-fifth, is very clearly demonstrated by this power. In 

 this object the definition of the fibres, as they ramify in various planes one 

 behind another, is remarkable ; and the flat appearance of the speci- 

 men as seen by the twenty-fifth, gives place to that of considerable depth 

 of tissue and perspective. The finest nerve-fibres ramifying in the cornea 

 and in certain forms of connective tissue are beautifully brought out by 

 this power, and their relation to the delicate processes from the connective- 

 tissue corpuscles can be more satisfactorily demonstrated than with the 

 twenty-fifth. The advantage of the fiftieth in such investigations seems 

 mainly due to its remarkable power of penetration. The angular aperture 

 of this glass is loO. Many twelfths have been made with a higher angu- 

 lar aperture, amounting to 1 70. 



It should be stated that the specimens of animal tissues which I have sub- 

 jected to examination by very high powers are mounted in strong syrup, or in 

 the strongest glycerine, according to the process detailed in ' How to work 

 with the Microscope,' 3rd edition, p. 204. It is perfectly true that no ad- 

 vantage results from examining by the aid of very high powers the tissues 

 of man and the higher animals immersed in water, or in fluids of which water 

 is the chief constituent; nor is it possible to make the specimen sufficiently 



