NATURAL PHILOSOPHY. 129 



long tubular follicles, opening into its cavity. Although the shells were par- 

 tially formed, the yolks had not yet descended into the duct; many of them 

 were nearly mature. If this be a normal state of things, then we have, thus 

 far, an unobserved example of the shell being formed previous to the de- 

 scent of the ovum. The shell forms a pocket, open at the upper extremity, 

 and through this opening, which is never wholly closed, the egg probably 

 descends into its cavity. 



NEW OBSERVATIONS ON ANIMAL ELECTRICITY. 



The structure of the eggs of birds offers a certain resemblance to some 

 forms of the galvanic battery, inasmuch as it consists of a fluid inclosed in 

 a porous diaphragm, and in contact with another fluid of a different chemi- 

 cal composition. This circumstance attracting the notice of Dr. John 

 Davy, he made it the subject of experiment, in order to ascertain whether 

 any galvanic action was exerted by the different constituents of which the 

 egg is composed. The result fully answered his expectations ; and there can 

 be little doubt that electro-chemical action plays an important part in the 

 changes which the egg undergoes during the process of incubation. Using 

 a delicate galvanometer and a suitable apparatus, on plunging one wire into 

 the white, and the other, insulated except at the point of contact, into the 

 yolk, the needle was deflected to the extent of 5; and on changing the 

 wires, the course of the needle was reversed. When the white and yolk 

 were taken out of the shell, and the yolk immersed in the white, the effects, 

 on trial, were similar, but not so when the two were well mixed; then no 

 distinct effect was perceptible. Indications also of chemical action were 

 obtained, on substituting for the galvanometer a mixture consisting of 

 water, a little gelatinous starch, and a small quantity of iodide of potassium, 

 especially when rendered very sensitive of change by the addition of a few 

 drops of muriatic acid. In the instance of newly-laid eggs, the iodine liber- 

 ated appeared at the pole connected with the white; on the contrary, in that 

 of eggs which had been kept some time, it appeared at the pole connected 

 with the yolk, answering in both to the copper in a single voltaic combina- 

 tion formed of copper and zinc. 



POLARIZED CONDITION OF MUSCULAR AND NERVE FIBRE. 



Mr. H. F. Baxter, in a paper in a recent number of the Edinburgh Neiu 

 Philosophical Journal, having arrived at the conclusion that the muscular 

 and nervous tissues arc during life in a peculiar state or condition, which 

 has been termed polarized, puts the following question: "Can this state, 

 dependent as it evidently is upon nutrition, be increased by any artificial 

 means?" That it may be diminished, or easily destroyed, is to be inferred 

 from the fact that, whatever interferes with the proper nutrition of a muscle 

 or nerve, or disorganizes their structure, Avhether by mechanical or chemical 

 agencies, destroys also the conditions upon which the existence of the mus- 

 cular or nerve currents depend; and it is, it may be observed, from the 

 manifestation of these currents that the existence of this polarized condition 

 is inferred. It is reasonable, therefore, to suppose, that it might be by the 

 employment of the electric force (or current) that we should perhaps obtain 

 some evidence to assist in solving this problem. 



We have not space for the details. The only conclusion (says the author) 



