BIOLOGICAL APPARATUS. 325 



" Muscle-Balance " (3,806) constructed and used, just forty years 

 ago, by the eminent anatomist and physiologist who laid the 

 foundations of Animal Histology. 



Du Bois Reymond has said of the experiments conducted by 

 the aid of this apparatus, that they were the first in which a vital 

 force was investigated by physical methods and gave results 

 capable of definite mathematical expression. 



No more striking proof of the progress of physiology since 1836 

 can be found, than is afforded by the numerous and varied instru- 

 ments for the quantitative determination of functional phenomena 

 of all descriptions gathered together in the present Exhibition. 



The relations of electricity to the properties of contractile and 

 nervous substance have led to the employment of the most deli- 

 cate apparatus of the electrician, as means of physiological inves- 

 tigation ; while it is not too much to say, that the introduction of 

 the various forms of registering apparatus has done for physiology 

 what the microscope has effected for anatomy. It has enabled an 

 apparently instantaneous action to be resolved into its successive 

 constituents, just as the microscope has analyzed an apparent 

 point into its co-existing parts ; while the elements of the most 

 complex co-ordinated movements have been separately deter- 

 mined, and their relations to one another accurately defined, 

 in a manner comparable to that in which the microscope renders 

 visible the complex arrangement of the histological elements of a 

 tissue, which to the unassisted eye appears homogeneous. 



The apparatus by which M. Marey has so successfully investi- 

 gated the phenomena of animal locomotion, affords an excellent 

 example of physiological appliances of this kind. 



The manner in which delicate physical and chemical apparatus 

 is applied to the investigation of such a function as respiration, 

 and to the illustration and explanation of the functions of the 

 higher senses, is well illustrated in the present Collection. 



The series of models, collections of specimens, and other 



