The NASA Johnson Space Center stratospheric dust collection program has made available to the scientific community a rare set of materials for studies of (1) extraterrestrial materials germane to the early history of the solar system and (2) natural and man‐made terrestrial materials in the stratosphere. A review of the first 291 cataloged particles provides a basis for a reliable taxonomy of all stratospheric particles. Data used in this review include particle shape, size, bulk chemistry, and texture. Extraterrestrial materials occur in all three defined categories: spheres, aggregates, and fragments. Approximately 76% of aggregates are of probable extraterrestrial origin. Spheres contain the least amount of extraterrestrial material (∼43%). A number of new groups of stratospheric particles have been identified. These include aluminum and silicate aggregates, aluminum fragments, and aluminum prime spheres and fragments. Limitations to the use of this classification scheme are based primarily upon the lack of additional data to unambiguously define particle origin.

Samples of a garnet granulitc from the mafic border units of the Lake Chatuge, Georgia alpine peridotite body were found to contain lamellar intergrowths of a pargastic amphibole in augite having the typical appearance of an exsolution feature. Single crystal X-ray diffraction, optical, electron microprobe and conventional and analytical electron microscopic studies have provided data limiting the compositions and structures of the coexisting phases. Individual tamellae of both materials are from 0.5 to 2.0 pm in width with the lamellar interface parallel to {010}. The formulae of the minerals, as determined by a combination of electron microprobe and analytical electron microscopy, are (Nao.lCal.oMgo.6Fe 3 +0.3)(Sii.sA10.2)O6 for the pyroxene and Nao.TCal.9(Mgz.lFe 2 + 1.4Fe 3 + o.sTio.lCro.lAlo.s)(Sis.9A12.1) O22(OH)2 for the amphibole. Several other studies have described intergrowths similar to those observed in this work, in general favoring exsolution as the formation mechanism for the intergrowths. In the Lake Chatuge samples however, replacement of pyroxene by amphibole is in part indicated by continuous gradation of amphibole lamellae into amphiboles rimming the clinopyroxenes.

A 4-year-old, 7-kg, female spayed Maltese dog was referred to the University of Missouri Veterinary Medical Teaching Hospital for acute onset of ataxia and left thoracic limb paralysis. The dog had been normal earlier that day when allowed outside but became ataxic and recumbent shortly after re-entering the house. She did not appear to be painful at that time. The dog had no prior history of illness and was current on all vaccinations.The general physical examination was within normal limits except for otitis externa and the findings related to the nervous system. Upon neurologic examination, spontaneous vertical nystagmus was noted. All other cranial nerves were normal. Proprioception was slightly decreased in the left pelvic limb, and the left thoracic limb was paralyzed and lacked nociception. Muscle tone and spinal reflexes were normal except for the left thoracic limb, which was areflexic and hypotonic. The dog was laterally recumbent and unable to stand. She displayed no discomfort when the paralyzed limb was palpated or manipulated through a full range of motion. Likewise, no hyperesthesia was noted along the length of the vertebral column or during manipulation of the neck.On the basis of the neurologic findings, multifocal disease affecting the left lateral cervical intumescence and caudal brainstem was suspected. A CBC and biochemical profile were performed to eliminate metabolic disease. Clinicopathologic abnormalities were limited to increased alkaline phosphatase (430 U/L; normal, 20-157 U/L). Differential diagnoses at this point for the acute onset of tetraparesis included spinal vascular disease, traumatic injury, coagulopathy, inflammatory disease (granulomatous meningoencephalitis, breed-specific encephalitis), or infectious diseases (eg, rickettsial, protozoal, viral).The dog's condition had not changed the next day, and additional diagnostics were performed. Under general anesthesia, a cerebrospinal fluid (CSF) tap at the L5-L6 vertebral junction was performed before a myelographic study. However, hemorrhagic contamination complicated the interpretation of the CSF sample, and the decision was made

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