24 Professor Burdon Sanderson [Jan. 24, 



should Le revived. Their contention amounts to little more than this, 

 that in certain recent instances improved methods of research appear 

 to have shown that processes, at first regarded as entirely physical or 

 chemical, do not conform so precisely as tbey were expected to do to 

 chemical and physical laws. As these instances are all essentially 

 analogous, reference to one will serve to explain the bearing of the 

 rest. 



Those who have any acquaintance with the structure of the animal 

 body will know that there exists in the higher animals, in addition to 

 the system of veins by which the blood is brought back from all parts 

 to the heart, another less considerable system of branched tubes, the 

 lymphatics, by which, if one may so express it, the leakage of the 

 blood-vessels is collected. Now, without inquiring into the why of 

 this system, Ludwig and his puj)ils made and continued for many 

 years elaborate investigations which were for long the chief sources 

 of our knowledge, their general result being that the efficient cause of 

 the movement of the lymph, like that of the blood, was mechanical. 

 At the Berlin Congress in 1890 new observations by Professor Hei- 

 denhain of Breslau made it appear that under certain conditions the 

 process of lymph formation does not go on in strict accordance with 

 the physical laws by which leakage through membranes is regulated ; 

 the experimental results being of so unequivocal a kind that, even 

 had they not been confirmed, they must have been received without 

 hesitation. How is such a case as this to be met ? The " Neovi- 

 talists " answer promptly by reminding us that there are cells, i.e. 

 living individuals, placed at the inlets of the system of drainage with- 

 out which it would not work, that these let in less or more liquid 

 according to circumstances, and that in doing so they act in obedience, 

 not to physical laws, but to vital ones — to laws which are special to 

 themselves. 



Now, it is perfectly true that living cells, like working bees, are 

 both the architects of the hive and the sources of its activity ; but if 

 we ask how honey is made, it is no answer to say that the bees make 

 it. We do not require to be told that cells have to do with the 

 making of lymph, as with every process in the animal organism ; but 

 what we want to know is how they work, and to this we shall never 

 get an answer so long as we content ourselves with merely ex- 

 plaining one unknown thing by another. The action of cells must 

 be explained, if at all, by the same method of comparison with 

 physical or chemical analogues that we employ in the investigation of 

 organs. 



Since 1890 the problem of lymph formation has been attacked by 

 a number of able workers — among others in London, by Dr. Starling 

 of Guy's Hospital, who, by sedulously studying the conditions under 

 which the discrepancies between the actual and the expected have 

 arisen, has succeeded in untying several knots. In reference to the 

 whole subject, it is to be noticed that the process by which difficul- 

 ties are brought into view is the same as that by which they arc 



