T. F. SMITH ON TRUE VERSUS FALSE IMAGES IN MICROSCOPY. 271 



tions of their discoverers. There is discordance enough, and Dr. 

 Abbe can only reconcile the differences by declaring that owing to 

 the nature of light itself no true knowledge of such structure is 

 possible. But is it not possible that something a little less potent 

 than the laws of light may be at fault, and lie sometimes with the 

 observers themselves ; that it may be possible to try to evolve a 

 type of structure out of the little bit of muscle under one's nose 

 without taking the precaution to see if under different conditions 

 the same substance may not assume different appearances ? The 

 cause of the difference of the appearance of muscular fibre I take 

 to be very simple, and to lie in its tendency to split into very 

 minute fibrils longitudinally, and into minute discs transversely, 

 and the displacement of the different parts under this process will 

 account for all the appearances, whether of beaded structure or 

 discs. Some of the fibrils are very minute indeed. I have 

 measured some not more than the 5 0^-00 °f an mcn m thickness. 

 Now imagine a bundle split up thus, and dividing at the same 

 time into minute discs transversely, and you must have the appear- 

 ance of a structure all beads. The single fibril under the Apochro- 

 matic is bent round on itself ; at the bend two of the discs con- 

 verge towards each other at the inner circumference, leaving a 

 wedge-shaped space between them. Assuming the discs to be a 

 denser material embedded in a soft medium, this is just what 

 would happen, and should be enough of itself to prove the appear- 

 ance truthful. Mr. Nelson claims to have discovered eight discs 

 in the space where I show six. To reject his evidence on that 

 particular bit of muscle would, I think, be unscientific, for surely 

 if a dark band can split into two small, there is no reason in itself 

 why it should not split into three smaller discs. 



To recur to Pleurosigma angulatwn. I will admit that there is 

 no particular reason why it presents the ordinary appearance, that 

 there is no connection here between structure and function. Con- 

 sidered as a silicious envelope for the vegetable cell, the pattern 

 might be arranged in twenty different ways without being less 

 suited to the purpose for which it was constructed. We may 

 have a reasonable belief that the appearance is truthful, but it 

 does not come home with that absolute conviction as some other 

 structures, which must be what they appear if the same natural 

 laws of force and resistance apply in microscopic structure as in 

 the larger world. Take the scales of butterflies and moths, for 



