Ciliary Motions in Reptiles and Warm-blooded Animals. 121 



We have, as already stated, discovered the general existence 

 of this property in reptiles, birds, and mammalia ; but, with all 

 our endeavours, we have never been able to detect any trace of 

 it in fishes. We examined, with this view, the feelers of the 

 Silurus, the gills, the mucous membranes of the head, the coats 

 of the intestines and swimming bladder, the kidneys with the 

 ureter, and the skin of many other fishes. Nor was any thing 

 of the kind visible in the embryo of Perca and Cyprinus, though 

 examined in various early stages of its development. 



b. Method of Investigation. 



As the vibratory motions occur on the whole surface of the 

 mucous membrane, in order to perceive them it is only neces- 

 sary to obtain a view of the membrane under a sufficiently 

 high magnifying power. In parts which have long cilia, such 

 as the commencement of the oviduct of birds, this may be ac- 

 complished by simply spreading out the portion of membrane on 

 the object-plate of the microscope, covering it with water, and 

 viewing it with the requisite power of the instrument. But it is 

 Ln genera] necessary to employ the following manipulation, in 

 order to perceive the phenomenon with certainty. 



The animal must be examined immediately after death. A 

 small piece is to be cut out from the membrane to be observed, 

 with a pair of fine curved eye-scissors, and folded on itself, in 

 such a manner that the edge of the fold shall be formed by the 

 free surface of the membrane, its adhering surface being now 

 inside and in contact with itself. The object is then to be pla- 

 ced in the microtomic compressor,* with a little water, and gent- 

 ly pressed, until the folded edge is brought clearly into view 

 under the microscope. Even this simple preparation is sufficient 

 to exhibit the phenomenon in great beauty ; but in order to ren- 

 der it still more conspicuous, a fluid is to be added, holding 

 small particles of some substance in suspension. Nothing an- 

 swers this purpose better than the black pigment of the eye dif- 

 fused in water; but the less experienced observer must be cau- 



* An instrument contrived or improved by Professor Purkinje, by which 

 two parallel glass plates can be gradually approximated, so as to compress a 

 soft object under the microscope to any required degree. 



7 



