1874.] On Magnets and Electric Conductors. 245 



quently hollowed by an extension into them of the cavity of the cell or 

 capillary, the partition between the two being finally absorbed. 



The best preparations for demonstrating the facts above described are 

 obtained from the subcutaneous tissue of the upper part of the fore limb, 

 and from that under the skin of the back regions in which, in the adult 

 rat, this tissue becomes almost entirely converted into fat. Even in the 

 new-born animal some portions have already undergone this change ; and 

 it is principally in the neighbourhood of such patches that the hsema- 

 poietic cells are met with. It is only when the young rats are not more 

 than a few days old that the formation of blood-vessels is preceded by a 

 development of blood-corpuscles within the same cells as form the vessels : 

 in such other animals as I have hitherto examined this phenomenon seems 

 to occur only whilst still in the foetal state. The immature condition in 

 which the young of the rat are brought forth is sufficient to account for 

 this difference. 



The observations here recorded as to the intracellular development of 

 blood-corpuscles are in many respects in accordance with what has already 

 been described by others as occurring in the area vasculosa and other parts 

 of the embryo chick. It has not, however, appeared desirable to enter 

 into the literature of the subject in this brief notice. 



III. " On the Attractions of Magnets and Electric Conductors." 

 By GEORGE GORE, F.R.S. Received January 27, 1874, 



Being desirous of ascertaining whether, in the case of two parallel 

 wires conveying electric currents, the attractions and repulsions were 

 between the currents themselves or the substances conveying them, and 

 believing this question had not been previously settled, I made the fol- 

 lowing experiment : 



I passed a powerful voltaic current through the thick copper wire of a 

 large electromagnet, and then divided it equally between two vertical 

 pieces of thin platinum wire of equal diameter and length (about six or 

 seven centimetres), so as to make them equally white-hot, the two wires 

 being attached to two horizontal cross wires of copper. 



On approaching the two vertical wires symmetrically towards the 

 vertical face of one pole of the horizontally placed magnet, and at equal 

 distances from it, so that the two downward currents in them might be 

 equally acted upon by the downward and upward portions respectively 

 of the currents which circulated round the magnet-pole, the one was 

 strongly bent towards and the other from the pole, as was, of course, 

 expected ; but not the least sign of alteration of relative temperature of 

 the two wires could be perceived, thereby proving that not even a small 

 proportion of the current was repulsed from the repelled wire or drawn 

 into the attracted one, as would have occurred had the attraction and 

 repulsion taken place, even to a moderate degree, between the currents 



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