BIOLOGY; 



OR, PHYSIOLOGY, ZOOLOGY, AND BOTANY. 



PROGRESS OF rUYSIOLOGY. 



Trof. Ilnxley delivered an address to the " Section of Bioloofy " 

 of the British Association, in 18GG, from which we extract the fol- 

 lowinnj: "The microscope has hitely been to i)hysi(>l<)f:jy much 

 wliat the steam-engine lias Ijetui to manufacture and transit. It 

 has opened up new regions for observation, and given an entirely 

 new direction to our thoughts. The structure of the several tis- 

 sues and organs has pruljabl}' been made out as far as the present 

 means permll, and we are occupied now in investigating their 

 mode of formation and connection with each other. Tliere seems 

 much reason to think that they are more closely related, more 

 continuous, than we have Ijeen in the habit of regarding them." 

 He goes on to speak of the probable continuity of tlie nerve 

 fibres and nerve vesicles — of the other parts of tiie nerves with 

 the tissues among which they ramify — of the areolar tissues with 

 serous, librous, and mucous membranes, and witli the structure 

 of tlie various organs, and with blood vessels. " We are thus re- 

 minded of the fact that, in their emiiryonic period, the several struc- 

 tures, or the potential rudiments of them, were all blended in a 

 liomogeneous germinal mass; and we learn that, though they 

 have become dift'erentiated, they have not become separated, 

 but retain, in their own mode of connection, the traces of their 

 common parentage and of their early continuity. Such a blend- 

 ing of ultimate tissue, as a remnant of embryonic condition, assists 

 us to explain many tilings, such as the transfer of imijressions 

 and what we call symi)athy. 



"We perhaps scarcely realize and appreciate the bearings of 

 the f:\ct, that all the various tissues are formed from a primitive 

 homogeneous and continuous plexus, by the formation and sep- 

 aration from one another of ' portions,' ' centres," ' masses,' 

 'cells,' or whatever we please to call them, and their develop- - 

 ment into structure. Attention has been directed almost exclus- 

 ively to the formation and development of these masses, and too 

 little to their separation ; though the latter is a process little, if at 

 all, less imijortant than the former, and must be effected by some- 

 thins: analogous to what we call abruption. Indeed, the work of 

 abruption, or hollowing out, during the embryonic state, is little 

 less active than that of secretion or building up. We are familiar 

 with its work in the formation of the areolar tissues and cavities 

 of lione, in the removal of the jjarts of the iris and ej^elids that do 

 not become developed into permanent structure ; but we are not 

 perhaps sufficiently impressed with the fact that the various cavi- 



