126 DR. KLEIN. 



B. The Ciliated Duct in the Rabbifs Tail. 



I am unable at present to add much to what I have already 

 published on this subject in my preliminary communication 

 in the * Centralblatt fiir Medicin. Wissenschaften/ 1871, 

 No. SS. 



If we cut off the tail of young or middle-sized rabbits near 

 the root, strip off the skin, and then tear off the joints 

 nearest the root from the rest of the tail (a well-known 

 method of isolating the delicate tendons of the tail), Ave often 

 succeed in isolating also what appears to the naked eye as a 

 yelloAvish cord, extending for nearly the whole length of the 

 tail. 



Under the microscope this is seen to be a duct, forming, in 

 all probability, a prolongation of the central canal of the 



fibres which spring off from the coarser ones, and which make a perivascular 

 plexus, and further, the still finer fibres which spring ofi" from this plexus. 

 If Beale with his " ultimate nerve-fibres," which I regard, as I have just now 

 stated, only as coarser nerve-fibres, deduces conclusions about the action of 

 nerves on the blood-vessels ; if Beale, while building theories, sets aside all 

 the most accomplished and laborious physiological researches of foreign 

 observers, I must pass that over, because I cannot follow him without 

 coming into collision with what has really been found to be the result of 

 experiments. Neither shall I discuss what Beale states about the structure of 

 the capillary vessels ; if Beale still adheres, only in a more refined sense, to the 

 description first given by Henle, ISil (' Allgemeine Anatomic,' p. J?91), that 

 also I pass by with great equanimity, the more so as our knowledge of the 

 structure of the capillary vessels has been brought by the numerous re- 

 searches of German histologists to such a point that the old view of Henle 

 must be regarded as a 'complete anachronism. Further, if Beale with his 

 method is not able to show anything more about the anatomical rela- 

 tions of the finer nerve-fibres than what he was already acquainted with 

 several years ago, and if he confesses that he is not able by his own method 

 to form any opinion about the assertions of other investigators obtained by 

 a different method — viz. by chloride of gold — and, therefore, doubts them ; I 

 should be the last to make any objection except by putting the facts 

 obtained by one method against the results of the other. If Beale, when 

 expressing these doubts, both orally and in writing, calls attention to the 

 fact that the non-meduUated nerves of the capillaries have been until lately 

 entirely passed over, I can only perfectly agree with him, especially since 

 Beale, as I stated above, many years since on several occasions described and 

 illustrated them by very beautiful figures. But, on the other hand, I must 

 allow myself to contradict Beale if he asserts that the doctrine of terminal 

 networks of non-meduUated nerve-fibres in general was, before him, un- 

 known in Germany, and that the networks of non-meduUated nerve-fibres 

 tchich he has described are now accepted, as I have been able to convince 

 myself that, although the doctrine of networks of non-medullated nerve- 

 fibres has been advanced by his researches in a very high and remarkable 

 degree, our knowledge of networks of non-medullated nerve-fibres in many 

 organs has had a different source than he has stated. (See my memoir in 

 the ' Month. Micr. Journ.,' April.) 



