1380.] Ossification of the Terminal Phalanges of the Digits. 71 



A recent paper by Dr. M. Kassowitz ("Die Normale Ossification, 

 etc.," in S. Strieker's " Medizinische Jahrbiicher," 1880), is accom- 

 panied by a plate (Taf. X), in which, there is diagrammatically repre- 

 sented a sagittal section through a finger of a human foetus of slightly 

 earlier age than fig. 2, infra. The cartilage of the terminal phalanx 

 is calcified at its distal extremity, and the calcified portion is en- 

 veloped in a thin cap of subperiosteal bone ; so that if allowance be 

 made for the diagrammatic nature of the figure, it affords a fair idea 

 of the actual condition of the phalanx as above described. Speaking 

 of this figure, however, the author says, " An der dritten Phalanx ist die 

 Yerkalkung schon bis an das distale Ende vorgedrungen, so dass nur das 

 der zweiten Phalanx zugekehrte Ende knorpelig geblieben ist. In 

 der That ist auch schon das gauze Endstuck mit einem periostal 

 gebildeten knochernen Ueberzuge versehen." (Op. cit., p. 279.) It is 

 evident from these words, that the author believes the ossification in 

 this phalanx to have begun at some point other than the distal end of 

 the shaft (presumably near its middle), and to have proceeded thence 

 at different rates towards the two extremities ; the only distinction 

 between this and the other phalanges being that here the area of 

 uncalcified cartilage at the distal end has quickly disappeared before 

 the advance of calcification from the centre of the shaft; while at the 

 proximal end the corresponding area still persists ; as it does at both 

 ends in ordinary cases. Farther on, he repeats this explanation, and 

 seeing the necessity of providing for the future growth of the bone at 

 its distal extremity, after the disappearance of the supposed cartila- 

 ginous head, he rightly assigns the entire task to the periosteum, 

 which has already enveloped the cartilage with its bony cap : — " In 

 der dritten Phalanx schwindet, wie wir friiher gesehen haben, der 

 Knorpel an dem distalen Ende vollstandig, indem die Yerkalkung 

 schon friihzeitig bis an die Oberflache vorriickt und auch die Kuppel 

 einen knochernen Ueberzug vom Periost aus bekommt, welches 

 letztere weiterhin auch das sehr geringe Langenwachstum an dem 

 distalen Ende besorgen muss." (Ibid., p. 280.) These extracts will 

 suffice to show that Dr. Kassowitz, while correctly describing the 

 appearances presented by the terminal phalanx in a certain stage of 

 its growth, has failed to draw the proper inferences from them. Had 

 he compared specimens of a somewhat earlier or later stage with the 

 one he has figured, he would probably have been led to recognise the 

 fact that the processes involved in the ossification of this bone spread 

 gradually backwards from the tip ; instead of, as he imagines, ad- 

 vancing rapidly towards it. 



