JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. When 18 months complete their growth, Then the tall canes' rich juices fill; And we, to bring their liquor forth, Convey them to the bruising-mill. That mill, our labour, every hour, Must with fresh loads of canes supply; And if we faint, the cart-whip's power, Gives force which nature's powers deny.A. Opie, The Black Man's Lament (1826), an antislavery tract for children. THIS STUDY IS CONCERNED WITH explaining some remarkable population patterns andwith examining the very extensive implications of these patterns. Among North American slaves, births greatly exceeded deaths, so that the slave population expanded rapidly. In sharp contrast, across the slave societies of the Caribbean and Latin America, the persistent experience was one not of natural increase but of dramatic natural decrease. Indeed, the North American pattern was probably, with a few local and sometimes short-term exceptions, unique in the history of slavery. As C. Vann Woodward wrote: "So far as history reveals, no other slave society, whether of antiquity or modern times, has so much as sustained, much less greatly multiplied, its slave population by relying on natural increase."' Why, then, did North American slaves experience such rapid natural increase (excess of births over deaths), and why did slaves in the rest of the Americas fail to increase naturally?The contrast between North America and the rest of the Americas is a fundamental one. For example, over the many years of the African slave trade, Jamaica imported some 750,000 slaves, but at the time of emancipation in 1838 its black population numbered only just over 300,000: North America, in contrast, imported only about 427,000 Africans, but at the time of emancipation in 1865 the U.S. black population had grown to more than ten times that number.2 In the antebellum period, U.S. slaves showed a natural population growth of some 25 percent per decade (and indeed, North American slaves had established a pattern 1 C. Vann Woodward, American Counterpoint: Slaveiy and Racism in the North/South Dialogue (Oxford, 1983), 91. 2 Philip D. Curtin, The Atlantic Slave Trade: A Census (Madison, Wis., 1968), 71. 1534 This content downloaded from 193.255.248.150 on Mon, 9 Feb 2015 07:01:36 AM All use subject to JSTOR Terms and Conditions The Demographic Cost of Sugar 1535 of natural growth by about 1710). In sharp contrast, Caribbean and Brazilian slaves commonly suffered rates of natural decrease of 20 percent per decade.3The North American slave experience is perhaps even more remarkable when compared with free white populations. From the later eighteenth century, and possibly before that even, and until the Civil War, the rate of natural growth of North American s...

Background In patients with phaeochromocytomas or paragangliomas (PPGLs), 24-h urine collections for metanephrines (uMNs) are cumbersome. Objective To evaluate the diagnostic utility of ratios to creatinine of ‘spot’ uMNs. Methods Concentrations of uMNs and plasma metanephrines (pMNs) were measured by HPLC-mass-spectrometry. We retrospectively compared correlations of 24-h-urine output and ratio to creatinine in historical specimens and prospectively assessed 24-h and contemporaneous spot urines and, where possible, pMNs. Using trimmed log-transformed values, we derived reference intervals based on age and sex for spot urines. We used multiples of upper limit of normal (ULNs) to compare areas under curves (AUCs) for receiver-operator characteristic curves of individual, and sum and product of, components. Results In 3143 24-h-urine specimens on 2416 patients, the correlation coefficients between the ratios and outputs of metanephrine, normetanephrine and 3-methoxytyramine in 24-h urines were 0.983, 0.905 and 0.875, respectively. In 96 patients, the correlations between plasma concentrations, urine output and ratios in spot specimens were similar to those for raw output or ratios in 24-h specimens. Of the 160 patients with PPGLs, the CIs for AUCs for individual metabolites overlapped for all four types of measurement, as did those for the sum of the multiple ULNs although these were slightly higher (AUC for spot urine: 0.838 (0.529–1), plasma: 0.929 (0.874–0.984) and output: 0.858 (0.764–0.952)). Conclusions Ratios of fractionated metanephrines to creatinine in spot urine samples appear to have a similar diagnostic power to other measurements. The ease of spot urine collection may facilitate diagnosis and follow-up of PPGLs through improved patient compliance.

Background The 24-h urinary output of 5-hydroxyindoleacetic acid (5-HIAA) is used to monitor disease progression and treatment responses of neuroendocrine neoplasms (NENs). Several conditions are required for 5-HIAA assay, involving urine collection/preservation and food/drug restrictions. Aim To evaluate the correlation between 5-HIAA concentration in a spot urine sample and the output in a 24-h urine collection, and whether spot urine specimens can replace 24-h collection. Methods Patients with NENs or symptoms suggestive of NENs were asked to provide a separate spot urine at the end of the 24-h urine collection for 5-HIAA assessment. The upper reference limit for 24-h urinary 5-HIAA was 40 µmol/24 h. 5-HIAA measurements in spot urine samples were corrected for variation in urine flow rate by expressing results as a ratio to creatinine concentration. Results We included 136 paired urinary samples for 5-HIAA assessment from 111 patients (100 NENs). The correlation between 5-HIAA values measured in 24-h and spot urines was r = +0.863 (P < 0.001) and r = +0.840 (P < 0.001) including only NEN patients. Using the 24-h urinary 5-HIAA as reference method, the AUC on ROC analysis for spot urinary 5-HIAA was 0.948 (95% CI, 0.914–0.983; P < 0.001), attaining a sensitivity of 83% and specificity of 95% using 5.3 mol/mmol as cut-off for the spot urine. The AUC among NEN patients alone was 0.945 (95% CI, 0.904–0.987; P < 0.001). Conclusions The ratio of 5-HIAA to creatinine in a spot urine could replace the measurement of 5-HIAA output in a 24-h urine collection, especially for follow-up of patients with known elevated 5-HIAA levels.