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IV. "Anatomical Notices." By Professor ANDREW RETZIUS, 

 of Stockholm. Extracted from a Letter to Dr. SHARPEY, 

 dated 10th May, 1855. Communicated by Dr. SHARPEY, 

 Sec. R.S. (Translation.} 



"1. On the Form of the Cranium in the Embryo. 



" So far as I am aware, due attention has not hitherto been given 

 to the different forms presented by the cranium in its earlier stages 

 of growth. In the skeletons of early human embryos to be seen in 

 most museums, the imperfectly ossified cranium is for the most part 

 shrunk up and disfigured. To obtain a correct view of the form of the 

 cranial cavity, I first remove the skin, fascia and muscles ; I then, by 

 injecting water through the vertebral canal, thoroughly wash out 

 the soft brain and spinal cord ; and lastly, fill the cerebro- spinal 

 cavity with quicksilver or with melted tallow, taking care not to 

 distend it over-much. The opening in the vertebral canal is to be 

 stopped with a little plug of wood, and the preparation allowed 

 to dry. 



" In the skeleton of a human embryo of the fourth month, pre- 

 pared in this way, the occipital bone was found to have the form of 

 a funnel, the narrow part of which passed into the vertebral canal, 

 as represented in the accompanying figure 1 . 



" It thus appears that the human occipital bone, in its early con- 

 dition, approaches in form to the vertebral canal, and in this respect 

 also it resembles the occipital bone in several quadrupeds, which so 

 obviously represents the first cephalic vertebra. 



" For the sake of comparison, I divided the skull of another em- 

 bryo of the same age into two halves by a vertical median section, 

 washed out the brain and examined the preparation while it lay im- 

 mersed in weak spirit of wine in a shallow glass capsule. The 

 occipital bone had the same funnel-shape as in the former case. As 

 development advances, the funnel-like form is gradually lost, whilst, 

 on the other hand, the bone appears more deepened or tubular the 

 earlier the embryo to which it belongs. The same is true of 

 quadrupeds. 



" In the beautiful figure of the embryo-skull, given in Kolliker's 

 ' Microscopische Anatomic,' B. II. tuf. 3. fig. 2, the downward pro- 



