ADDRESS BEFORE TEE BRITISH ASSOCIATION. 565 



these and other observers the most salient and, if I may use the ex- 

 pression, the grosser characters of animal organization had been recog- 

 nized, little was known of the more intimate structure or texture of the 

 parts. So far as could be determined by the unassisted vision, and so 

 much as could be recognized by the use of a simple lens, had indeed 

 been ascertained, and it was known that muscles, nerves and tendons 

 were composed of threads or fibers, that the blood and lymph-vessels 

 were tubes, that the parts which we call fasciae and aponeuroses were 

 thin membranes and so on. 



Early in the present century Xavier Bichat, one of the most brilliant 

 men of science during the Napoleonic era in France, published his 

 'Anatomie Generale/ in which he formulated important general prin- 

 ciples. Every animal is an assemblage of different organs, each of 

 which discharges a function, and acting together, each in its own way, 

 assists in the preservation of the whole. The organs are, as it were, 

 special machines situated in the general building which constitutes the 

 factory or body of the individual. But, further, each organ or special 

 machine is itself formed of tissues which possess different properties. 

 Some, as the blood-vessels, nerves, fibrous tissues, etc., are generally dis- 

 tributed throughout the animal body, whilst others, as bones, muscles, 

 cartilage, etc., are found only in certain definite localities. While 

 Bichat had acquired a definite philosophical conception of the general 

 principles of construction and of the distribution of the tissues, neither 

 he nor his pupil Beclard was in a position to determine the essential 

 nature of the structural elements. The means and appliances at their 

 disposal and at that of other observers in their generation were not suffi- 

 ciently potent to complete the analysis. 



Attempts were made in the third decennium of this century to im- 

 prove the methods of examining minute objects by the manufacture 

 of compound lenses, and, by doing away with chromatic and spherical 

 aberration, to obtain, in addition to magnification of the object, a rela- 

 tively large flat field of vision with clearness and sharpness of definition. 

 When in January, 1830, Joseph Jackson Lister read to the Eoyal 

 Society his memoir "On Some Properties in Achromatic Object-Glasses 

 Applicable to the Improvement of Microscopes," he announced the prin- 

 ciples on which combinations of lenses could be arranged, which would 

 possess these qualities. By the skill of our opticians, microscopes have 

 now for more than half a century been constructed which, in the hands 

 of competent observers, have influenced and extended biological science 

 with results comparable to those obtained by the astronomer through 

 improvements in the telescope. 



In the study of the minute structure of plants and animals the ob- 

 server has frequently to deal with tissues and organs, most of which 

 possess such softness and delicacy of substance and outline that, even 



