398 DR. R. W. SHUFBLDT ON 



instance, as I say, such as has occurred in the patella shown in 

 PI. LXI. fig. 11 and others. It must stand to reason, then, that 

 Garrod entertained an untenable opinion in this matter. 



Coming to the second way in which this foramen could have 

 been formed, it is clear that, in young and subadalt individuals, 

 the tendon of the ambiens muscle could be confined by an 

 additional piece of bone or cartilage being placed in front of it, 

 and this added part subsequently ossify and not only form, in 

 the adult, a foraminal passage for the aforesaid muscle or its 

 tendon, but largely add to the bulk of the patella. It might, too, 

 — from the thoroughness of the coossification — cause the atrophy 

 of the muscle and its tendon at that part of the course of the 

 latter across the front of the true patella ; and such a result would 

 be brought about by the entire sealing up of the foraminal 

 passage, which not only actually takes place in the patellse of 

 some Cormoi'ants, but again proves Garrod to have been wrong 

 when he stated that such a foramen or foraminal passage was 

 always present in the patella of Cormorants. See PI. LXI. 

 fig. 3 — Fhalacrocorax jpeiiicillatus — whei-e it has been sealed up 

 entirely, leaving not so much as a trace or a suspicion of its ever 

 having been present there. 



In my opinion, the foraminal passage for the ambiens muscle, 

 passing transversely through the patella in the Phalacrocoracidse, 

 when pi-esent, is formed as set forth below, which formation can 

 be demonstrated by the material figured in the plate accompanying 

 this paper. When the foraminal passage is entirely absent it 

 has been absorbed, atrophy of the ambiens probably having 

 ensued. 



It would appear that in young Cormorants the ambiens passes 

 in a groove, of the required depth only, obliquely across the 

 anterior face of the patella, which latter is very closely adpressed 

 against the posterior surface of the long cnemial process of the 

 tibio-tarsus, — a condition that persists throughout life in Grebes 

 (Colymbidfe). Coossification between the patella and the upper 

 two-thirds of the cnemial process of the tibio-tai-sus, in the case 

 of the growing Cormorant, next sets in, which, owing to the 

 morphology of the parts involved, would, in time, depreciate 

 the action of the knee-joint. This is clear when we come to 

 consider the origins and insertions of the various muscles about 

 the knee-joint anteriorly, posteriorly, and laterally*. These, 

 during their continued action in locomotion — especially during 

 the act of swimming — tend to overcome the aforesaid danger, 

 militating against the complete freedom of action of the knee- 

 joint. Coossification steadily proceeds ; the individual grows ; a 

 constant tugging is exerted during locomotion at the tibio-tai-sal 

 cnemial apophysis. This eventually results in its becoming 

 dissociated from the bone to which it belongs along a transverse 

 line, at a short distance above the level summit of the tibio- 

 tarsal shaft, thus leaving the lower third of the cnemial 



* Slmfcldt, K. W. ' The Myology of the Raven/ p. 187, figs. 51-53, London 

 1890. i 



