308 THE SCIENCE OF MICROSCOPY. 



peculiar to the microscope as an optical instrument, belong to the 

 rationale of its image-forming function, though their occurrence be 

 primarily due to the presence and influence of the organic 

 structures, or inorganic molecules examined. Many of these 

 phenomena form no part of the special attributes of the structure 

 conditioning them, but are referable to the nature and properties 

 of light, and to the action of the reflecting and refracting media of 

 the microscope. Here therefore we find a special sphere of 

 observation — a science of microscopy — resting on genuine found- 

 ations. For the possible fact or fiction presented to the eye through 

 the microscope, can only be converted into scientific building 

 material by a critical reasoning process, involving, firstly, the 

 performance of the lenses -, and secondly, the physical condition 

 of the object, as well as the manner of its presentment, consequent 

 upon modes of illumination. If then a regulated culture of the art 

 of observing microscope effects is unattainable, except by an 

 exhaustive study of the optical characteristics of the images 

 produced by the microscope, and of the various attendant circum- 

 stances which can only be explained on physical and physiological 

 grounds, it is a mere evasion of this position to assert that familiarity 

 with the instrument, and a certain training in the proper manage- 

 ment of the illumination (supposed to be acquired by habit and use) 

 are all that is needed for a successful practice of microscopy, and a 

 right interpretation of what is seen. For since the microscope 

 exhibits but a counterfeit (more or less accurate) of the object 

 itself, its '' revelations'' depend upon our mental grasp of what we 

 see, or seem to see. And we can only turn our seeing into 

 perceiving, by an" intelligent interpretation of the shadow which has 

 been substituted for the substance. But the "^ practical" micro- 

 scopist, having relegated all study of the theory of the microscope 

 to the practical optician, and the physico-mathematical researches 

 connected with it to the " theorist," only gives his attention as an 

 observer to the details presented to his mind, in connection with 

 the naturalistic aspect of the object (or the shadow-image of it). 



