586 



PHYSIOLOGY. 



of the pulp, these fibers meeting over the dentinal 

 end of the odontoblasts so as to form a thin 

 fibrous layer between these cells and the dentine 

 matrix. The matrix is supposed by the author 

 to be secreted by the odontoblasts into this layer 

 of tissue. 



As results of his studies of the development 

 of the primordial cranium, Dr. Giuseppe Levi, of 

 Florence, concludes that the first rudiments of 

 the primordial cartilaginous cranium in man oc- 

 cur in the form of isolated groups of closely com- 

 pressed connective-tissue cells in looser tissues 

 than that which forms the membranous primor- 

 dial cranium. A certain homology appears be- 

 tween these aggregations of cell groups and those 

 of the future bone; but there is no homology be- 

 tween these rudiments of the skull of man and 

 those described in mammals as parachordals and 

 trabecuhe. The rudiments preserve their identity 

 for some time, even after their conversion into 

 cartilage, by the possession of a perichondrial 

 layer. They do not all coalesce till just before 

 the chondrocranium has attained its highest 

 development, when the chondrocranium for the 

 first time forms one continuous whole. In the 

 order of formation of the rudiments formed by 

 connective tissue, that of the occipital bone is the 

 earliest; after it follow those of the sphenoid and 

 of 'the auditory capsules ; and lastly that of the 

 ethmoid. The differentiation of the several rudi- 

 ments, progressing with unequal rapidity, is, as 

 a rule, most rapid in the latest formed parts, 

 and it presents characteristic features in each 

 case, advancing quickly in the occipital region 

 and almost contemporaneously throughout its 

 whole extent, while in other instances it begins 

 at a definite spot in a kind of cartilaginous 

 nucleus and spreads uniformly outward. The en- 

 largement of the rudiments is at first rapid, but 

 afterward extremely slow. The development of 

 the occipital region is similar to that of the ver- 

 tebral column. The histological features of the 

 formation of cartilage are particularly identical 

 with those of this column, while they are differ- 

 ent from those of all other segments of the skull. 

 Moreover, there is one distinct rudiment of a ver- 

 tebra the occipital which has a symmetrical 

 origin, and farther forward are parts of an. in- 

 determinate number of vertebrae. The occipital 

 region, like the vertebral column in the first 

 stages of its development, is in connection with 

 the chorda, but becomes distinct from it as the 

 cartilage develops. These facts support Froriep's 

 view that the occipital region represents the true 

 spinal segment of the skull in man. " The sym- 

 metrical rudiments of the body of the occipital ver- 

 tebra become the condyles of the occipital, the un- 

 scL'tuented portion represents the portio basilaris, 

 and the lateral portion of the arch of the occipital 

 vertebra the processus jugularis." Some changes of 

 form take place in the development of cartilage 

 through the absorption of parts of the rudiments 

 and through alteration of the position of the 

 occipital and sphenoid rudiments; and the floor 

 of the sella turcica is the only segment of the 

 skull which preserves its original position 

 throughout the process of development. 



In the preliminary experiments made by W. S. 

 Halliburton for the purpose of testing the con- 

 flicting results reached by other investigators of 

 the effects of injections of extracts of nervous 

 tissues, all the extracts used produced a fall of 

 blood pressure, partly by their effect on the 

 heart, and partly by dilatation of vessels in the 

 splanchnic area. The effect was more marked 

 tlie greater the proportion of gray matter in the 

 tissue used. It was not abolished by the section 



of both vagi, but was abolished, as a rule, after 

 atropine. The substance that produced the tall 

 was not proteid, but was soluble in alcohol. 

 From the alcoholic solution the author always 

 obtained typical crystals of the platinum double 

 salt of choline. Though the choline thus proved 

 to be present w r as undoubtedly one cause of the fall 

 in blood pressure, there were probably other sub- 

 stances that might be present as well, but they 

 had not yet been fully identified ; lactic acid was 

 probably one. The depressor effect of lactic acid 

 was not abolished by atropine; and this fact, it 

 is suggested, may account for those cases in 

 which the fall was not completely abolished by 

 that substance. Glycerin itself (1 in 20 of saline 

 solution) generally produces a fall of blood pres- 

 sure, which is not abolished by atropine. 



The name spermine is given to certain needle- 

 shaped crystals which Charcot observed for the 

 first time in the blood of leuko-erythemics, which 

 Leyden had discovered in the expectoration of 

 asthmatics, and which Schreiner found in sperm. 

 and which were analyzed, identified, and charac- 

 terized by Poehl. The object of a research by 

 Walter E. Dixon was to ascertain the effect of 

 injections of spermine in order to determine how 

 far the substance is responsible for the effects pro- 

 duced by injections of Brown-Sequard's fluid. It 

 was shown by experiments made on cats that 

 spermine produces a fall of blood pressure from 

 which recovery is rapid and the normal level 

 is soon reached. The effect is largely cardiac, 

 but is also partly due to dilatation of vessels in 

 the splanchnic area. The effect of the use of 

 atropine is to cut out completely the fall of pres- 

 sure, without, however, influencing the splanchnic 

 dilatation. The vessels of the kidneys seem quite 

 passive to the change of blood pressure. The 

 effect on the splenic vessels is marked by the con- 

 striction of the splenic muscle. A stimulant 

 effect on the involuntary muscles of mammalian 

 intestine as well as on the isolated strip of frog's 

 stomach is also noticeable. Spermine produce?- a 

 gradual rise in the body temperature. A close 

 resemblance exists in the effects upon the heart 

 and circulatory system of the action of choline 

 and of spermine, and the two substances are 

 about equally toxic. The chief interest of sper- 

 mine depends on the fact that it is constantly 

 present in all tissues of the body, and in certain 

 pathological conditions (leuko-erythemia and 

 some nervous diseases) is increased. It is said 

 to be present in the normal animal in greatest 

 quantity in the testis and nervous tissue. 



The presence of arsenic in the body has been 

 studied by M. Armand Gautier, who communi- 

 cated a paper on the subject to the French Acml- 

 emy of Sciences, Dec. 4. The author found this 

 substance normally present in the thyroid gland 

 in the proportion of 0.075 milligramme to 100 

 grammes of the dried gland. It is found also in 

 the skin, hair, and nails, and in ox horns; in tin 

 mammary gland, and consequently in the milk 

 which it elaborates. The brain of the fuMus eon 

 tains arsenic, as also does the brain of the ne\vl\ 

 born infant, but no trace of it was found in the 

 adult brain of hospital patients. It also occur-' 

 in the bones, but was not found in the liver, pan 

 creas, kidney, spleen, pituitary gland, stomach, 

 and intestines. The last fact is of considerable 

 importance, as it bears upon toxicological 

 searches, for there results from it as an imme- 

 diate consequence that if arsenic is found a'. 

 any time in the stomach or an intestine it is no; 

 normal. 



The remarkable changes made in recent yi-ar; 

 in the diameter and velocity of rifle bullets havi; 





