A Biological Application of Röntgen Photography

Abstract

THE accompanying Röntgen radiograph of Astropecten irregularis was made in the physical department of this college, for a popular lecture on the new photography given by Prof. H. Stroud. It will be seen that not only are the ossicles of the oral surface fairly successfully shown through the thickness of the body and arms, markedly the first of the series of adambulacra, but certain striking and unlooked-for objects appear as well. On dissection the dark conical body to the right proves to be a large piece of the shell of Dentalium lying in one of the cæca of that arm. The oval bodies, one in each of the cæca of the opposite arm, are masses of sand and indigestible material enclosed in the thinned shells of molluscan victims. These are made by the action of the cilia, and form a convenient way of getting rid of the useless matter by way of mouth. The minute anus, indeed, is quite inadequate, and is doubtless used more for fluid than solid evacuation. The madreporite plate and stone canal are seen in the inter-radius below and between the bodies referred to; and the position of the stone canal was in fact the guide in determining their position. The darkish mass in the cæcum to the left of the stone canal consists mainly of broken and whole shells of young Cardia. The stomach was filled with a whole common mussel (Mytilus edulis), minus the shell, and this is quite transparent. The paxillæ will be seen to occur as dots all over the body and arms. A block of wood, which was laid over part of the star-fish, has evidently only made a part of the picture lighter.