74 THE MICROSCOPE. 



favour of tlie spontaneous generation tlieory, may pro- 

 bably be studied with some advantage. 'Not only are the 

 minuter atoms too small to be studied by the T^th or xVth, 

 but particles too transparent to be observed by the ^V^h 

 are, according to Dr. Eeale, distinctly demonstrated by 

 the ■g'jjth ; he observes, " I feel sure that further careful 

 study, by the aid of these high powers, of the develop- 

 ment and increase of some of the lowest organisms, and 

 the movements which have been seen to occur in certain 

 forms of living matter (amoeba, white blood-corpuscles, 

 young epithelial cells, &c.), will lead to most valuable 

 results, bearing u^Don the much debated question of vital 

 actions. 



" The most delicate constituent of the nerve-fibres of 

 the plexus in the summit of the papilla (see Fhil. 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 diawing they would be represented by fine 

 single lines. JS^ear the summit of the papilla there is a 

 very intricate interlacement of nerve-fibres, which, although 

 scarcely brought out by the ^sth, is very clearly demon- 

 strated by this power. In this object, the separation of 

 the fibres, as they ramify in various places, one behind 

 another, is remarkable, and the flat appearance of the 

 specimen as seen by the -^ih. gives place to tliiit of con- 

 siderable depth of tissue and perspective. The finest 

 nerve-fibres, ramifying in the cornea of the eye, and in 

 certain forms of connective tissue, are beautifully brought 

 out ; and their relation to the delicate processes from the 

 connective-tissue corpuscles can be more satisfactorily 

 demonstrated than l)y the ^gth. The advantage of the 

 5\yth in such investigations seems mainly due to its re- 

 markable power of penetration." 



The one great drawback to the use of this objective, 

 and a very serious one to most microscopists, is its costli- 

 ness. The price of this power alone is almost more than 

 many can afford to give for a complete instrument. 



In flatness of field, and in perfection of definition, botli 

 at the centre and margin of the field of view, few ol)]'ec- 

 tives have equalled the recent y-^-th of Mr. Eoss, who 

 appears to have inherited his late Jather s well-known skill 



