Sentence:  The essence of a tandem team is surely that it should be well balanced, sporting in appearance and that the horses themselves should at all events convey the impression of being able to do a long stage with ease and comfort. Now there can be nothing "sporting" about a beefy, <WSD>bosomy</WSD>, bad-shouldered tandem leader, who picks his fore feet up as high as he can, hangs them down again with a straight thrust on the ground, but a very little distance in advance of the spot from which he took them up. 
Meaning of the word marked with <WSD> tags:  Having a large bosom.