360 



SCIENCE. 



[N. S. Vol. XII. No. 297. 



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, and that the parts which we call 

 fasciae and aponeuroses were thin mem- 

 branes, 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 

 principles. Every animal is an assemblage 

 of different organs, each of which dis- 

 charges a function, and acting together, 

 each in its own way, assists in the preser- 

 vation of the whole. The organs are, as 

 it were, special machines situated in the 

 general building which constitutes the fac- 

 tory or body of the individual. But, fur- 

 ther, each organ or special machine is 

 itself formed of tissues which possess dif- 

 ferent properties. Some, as the blood-ves- 

 sels, nerves, fibrous tissues, etc., are gen- 

 erally distributed throughout the animal 

 body, whilst others, as bones, muscles, car- 

 tilage, etc., are found only in certain defi- 

 nite localities. Whilst 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 struc- 

 tural elements. The means and appliances 

 at their disposal and at that of other ob- 

 servers in their generation were not suffi- 

 ciently potent to complete the analysis. 



Attempts were made in the third decen- 

 nium of this century to improve the meth- 

 ods of examining minute objects by the 

 manufacture of compound lenses, and, by 

 doing away with chromatic and spherical 

 aberration, to obtain, in addition to magni- 

 fication of the object, a relatively large flat 

 field of vision with clearness and sharp- 

 ness 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 principles on which combinations of 

 lenses could be arranged, which would pos- 

 sess 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 with those obtained 

 by the astronomer through improvements 

 in the telescope. 



In the study of the minute structure of 

 plants and animals the observer has ire- 

 quently to deal with tissues and organs, 

 most of which possess such softness and 

 delicacy of substance and outline that, even 

 when microscopes of the best construction 

 are employed, the determination of the in- 

 timate nature of the tissue, and the precise 

 relation which one element of an organ 

 bears to the other constituent elements, is 

 in many instances a matter of difBculty. 

 Hence additional methods have had to be 

 devised in order to facilitate study and to 

 give precision and accuracy to our observa- 

 tions. It is difiicult for one of the younger 

 generation of biologists, with all the appli- 

 ances of a well- equipped laboratory at his 

 command, with experienced teachers to di- 

 rect him in his work, and with excellent 

 text-books, in which the modern methods 

 are described , to realize the conditions under 

 which his predecessors worked half a cen- 

 tury ago. Laboratories for minute biolog- 

 ical research had not been constructed, the 

 practical teaching of histology and embry- 

 ology had not been organized, experience 

 in methods of work had not accumulated ; 

 each man was left to his individual efforts, 

 and had to puzzle his way through the 

 complications of structure to the best 

 of his power. Staining and hardening 

 reagents were unknown. The double- 



